assignment Flashcards by S W

If the spontaneous polarization of a ferroelectric material decreases continuously as the temperature increases from below to above Curie temperature, the material is undergoing a first-order phase transition. (T/F)

False

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The orientational polarization due to a permanent dipole will not contribute to the dielectric constant of a material under a high frequency in the visible range. (T/F)

TRUE

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BaTiO3 is a perovskite material. It possesses a cubic unit cell above the Curie temperature, with the Ti atom located at ___ of the cubic unit cell.
a. body center
b. face center
c. corner
d. random position

a. body center

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A parallel plate capacitor is originally empty between the two metal electrodes. A dielectric material is then inserted into the empty space between the two electrode. The capacitance is then ____?
a. increased
b. unable to determine
c. unchanged
d. decreased

a. increased

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A dielectric material normally has a dielectric constant greater than 1. (T/F)

True

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When the temperature of ferroelectric PZT material is above the Curie temperature, the PZT is in a ____ phase.
a. antiferroelectric
b. paraelectric
c. ferroelectric
d. dielectric

b. paraelectric

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The direction of a dipole moment is pointing from the positive charge to the negative charge of the dipole. (T/F)

False

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The volumetric energy density of a parallel plate dielectric capacitor will be increased if the thickness of the capacitor is decreased. Assume the electric field applied to the capacitor remains unchanged. (T/F)

False

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Increasing the surface area of a supercapacitor can result in a higher capacitance. (T/F)

True

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The cyclic voltammetry (CV) curve of an ideal electric double layer capacitor should be in a(n) _____ shape.
a. triangular
b. circular
c. rectangular
d. irregular

c. rectangular

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The iR voltage drop in a GCD curve is related to the equivalent series resistance of a supercapacitor. (T/F)

True

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The electrochemical performance of an electrode material can be evaluated by a three-electrode system. (T/F)

True

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Merely decreasing the distance between the positive and negative electrodes of an electrochemical supercapacitor can increase its capacitance. (T/F)

False

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The Galvanostatic charge discharge (GCD) curve of an ideal electric double layer capacitor should be in a(n) _____ shape.
a. triangular
b. rectangular
c. irregular
d. circular

a.trianglar

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If the charge storage mechanism of a supercapacitor is the solid-state diffusion of ions, the voltammetry current in the CV curve is proportional to v^n. Here v is the voltage scan rate and n is _____.

1/2

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Which of the following electrolytes can be used in lieu of a separator in a supercapacitor?
a. Solid-state electrolyte
b. Organic electrolyte
c. Ionic liquid electrolyte
d. Aqueous electrolyte

a. Solid-state electrolyte

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In a cyclic voltammetry measurement, which of the following quantity is kept constant?

Voltage Scan Rate (dV/dT)

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In general, which of the following types of electrolyte has the highest ionic conductivity?

Aqueous electrolyte

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A Galvanostatic charge discharge (GCD) curve is measured under a constant _________.

current density

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An electrochemical supercapacitor normally has a higher energy density than a lithium-ion battery. (T/F)

False

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A separator is indispensable for a solid-state lithium battery. (T/F)

False

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Which of the following component in a lithium-ion battery uses Aluminum foil?
a. Current collector on the anode side.
b. Anode.
c. Current collector on the cathode side.
d. Cathode.

c. Current collector on the cathode side.

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Copper cannot be used as the current collector for anode of a lithium-ion battery. (T/F)

False

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LiCoO2 has a three-dimensional framework for the diffusion of Li ions. (T/F)

False

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In graphite material, theoretically, how many carbon atoms can accommodate the insertion of one Li ion? a. 5 b. 6 c. 4 d. 7

b.6

During discharge, Li ions intercalate into the LiCoO2 cathode. (T/F)

True

Lithium-ion capacitors embody both the advantages of lithium-ion batteries and electrochemical supercapacitors. (T/F)

True

A lithium-ion battery is discharged at a rate of 2C. How long will it take for this battery to be fully discharged under this rate?

0.5 hours

In a Li-S battery, the polysulfide intermediates Li2Sx (x=4-8) are insoluble in electrolyte. (T/F)

False

Which of the following materials belongs to NCM cathode material for lithium-ion batteries? a. LiCoO2 b. LiMn2O4 c. LiNi0.8Co0.1Mn0.1O2 d. LiFePO4

c. LiNi0.8Co0.1Mn0.1O2

The storage of Li in graphite belongs to the conversion reaction mechanism. (T/F)

False

The Li ion diffusion in LiMn2O4 is ___. a. one dimensional b. two dimensional c. three dimensional d. unable to determine

c. three dimensional

Which of the following ions are conducted through the electrolyte of a direct methanol fuel cell? a. H+ b. OH- c. O^2- d. CO3^2-

a. H+

Which material below is the best for an SOFC electrolyte? a. La1-xSrxGa1-yMgyO3-d (LSGM) b. graphite c. H2 d. O2

a. La1-xSrxGa1-yMgyO3-d (LSGM)

Y-doped zirconia (YSZ) is used as ____ in a solid oxide fuel cell.

electrolyte

In an SOFC, the thermal expansion coefficients of cathode, anode and electrolyte should be matched. (T/F)

True

ORR is a two-electron process. (T/F)

False

Which of the following ions are conducted through the electrolyte of a molten carbonate fuel cell? a. OH- b. H+ c. O^2- d. CO3^2-

d. CO3^2-

As an SOFC electrolyte, YSZ should work at a lower temperature than GDC. (T/F)

False

In the temperature range of 600-1000°C, the ionic conductivity of YSZ _______. a. increases with increasing temperature b. decreases with increasing temperature c. is independent of temperature d. first increases then decreases with temperature

a. increases with increasing temperature

Alkaline fuel cells are sensitive to CO2. (T/F)

True

In the Nernst equation, the activity of solute ions in an ideal solution is normally taken as _____. a. 0.5 b. the concentration ratio of that solute ions to the standard concentration c. 1 d. 0.1

b. the concentration ratio of that solute ions to the standard concentration

Both of the cathodic and anodic polarizations will contribute to the voltage loss during the operation of a fuel cell. (T/F)

True

The electronic conductivity of an SOFC electrolyte should be kept high, while the ionic conductivity should be kept low under working condition. (T/F)

False

Under a forced oscillation, a material will have the largest deformation when the frequency of applied force equals the resonance frequency of the material. (T/F)

True

The working principle of a quartz crystal microbalance is based on the mass-dependent resonance frequency.

True

We use piezoelectric constant to evaluate the polarization developed on the surface of a ceramic sample due to the application of an electric field. If the electric field is along z-direction and we are interested in the polarization developed in this direction, which of the following piezoelectric constant should be used? A. d15 B. d33 C. d13 D. d12

B. d33

PZT is a piezoelectric material whose Curie temperature depends on the ratio of PbZrO3 and PbTiO3 (T/F)

True

Triboelectric nanogenerator (TENG) outperforms a conventional electromagnetic generator particularly in the high frequency range. (T/F)

False

For geothermal power stations that use the binary cycle design, the substance that drives the turbine usually has a boiling temperature higher than 100°C. (T/F)

False

Which of the following factor should be matched for the materials connected in series in the design of segmented thermoelectric generators? A. Current density B. Thermal flus C. Compatibility factor D. Carnot efficiency

C. Compatibility factor

The “phonon-glass and electron-crystal” strategy for thermoelectric materials means “low thermal conductivity and high electronic conductivity”.

True

In general, the mean-free path of electrons of a thermoelectric material is shorter than the mean-free path of phonons.

True

Which material below is the best for a thermoelectric device? a. Carbon fiber reinforced composite b. CH3OH (Methanol) c. LM4X12 (Skutterudite) d. La1-xSrxGa1-yMgyO3-d (LSGM) e. Pb(ZrxTi1–x)O3

c. LM4X12 (Skutterudite)

Working between the same hot and cold heat reservoirs, the efficiency of a thermoelectric device can never exceed that of a Carnot engine.

True

In order to have a higher figure of merit, a thermoelectric material should have ____ a. higher electric conductivity but lower thermal conductivity. b. lower electric conductivity but higher thermal conductivity. c. lower electric conductivity and lower thermal conductivity. d. higher electric conductivity and higher thermal conductivity.

a. higher electric conductivity but lower thermal conductivity.

The Seebeck coefficient of an n-type semiconductor is positive. (T/F)

False

Normally, a thermoelectric device has a higher efficiency than an engine at lower power level. (T/F)

True

A higher binding energy per nucleon (BEN) of an atom means that atom is less stable. (T/F)

False

Which material below is the best for the cladding of nuclear fuel in a fission reactor? A. 235U B. Zr-based alloy C. light water D. heavy water

B. Zr-based alloy

Which of the following statement is true in a radioactive decay of nuclei? A. The linear momentum is conserved. B. The angular momentum is conserved. C. The total energy is conserved. D. All of the aboves.

D. All of the aboves.

Which material below is the best for a nuclear fission reaction? A. 1H B. 2H C. 3H D. 235U

D. 235U

The binding energy per nucleon (BEN) of 56Fe is higher than that of 235U. (T/F)

True

When YSZ is utilized as the top coat of thermal barrier coating for gas turbines in a coal-fired power plant, which of the following property of YSZ is considered NOT important? A. Ionic conductivity. B. Thermal conductivity. C. Mechanical strength. D. Structural stability.

A. Ionic conductivity.

The reaction products of water-gas shift reaction are CO and H2. (T/F)

False

Which of the following conditions is the best for hydrogen storage in MOF materials? a. High temperature and high pressure. b. High temperature and low pressure. c. Low temperature and high pressure. d. Low temperature and low pressure.

c. Low temperature and high pressure.

In a conventional ceramic membrane for CO2 separation, which of the following is responsible for the gas separation? A. Porous substrate with pore size over 50 nm. B. Interlayer with pore size less than 50 nm. C. Top silica layer with pore size in the range of 0.3-0.5 nm. D. None of the above.

C. Top silica layer with pore size in the range of 0.3-0.5 nm.

Carbon sequestration refers to the capture and secure storage of CO2. (T/F)

True

The Volmer step is the first step in HER, no matter in acidic or alkaline medium. (T/F)

True

Although hydrogen gas has a high gravimetric energy density, its volumetric energy density is low (T/F)

True

Which of the following is NOT a carbon capture method in a coal-fired power plant? A. Pre-combustion. B. Middle-combustion. C. Post-combustion. D. Oxy-combustion.

B. Middle-combustion.

For photocatalytic full water splitting, the conduction band minimum should be more negative than the theoretical HER potential. (T/F)

True

Which of the following is the first OER step in an acidic medium? “*” stands for active site of the catalyst. a. *O + H2O → *OOH + H+ + e- b. *O2 → * + O2 c. * + H2O → *OH + H+ + e- d. *OH → *O + H+ + e-

c. * + H2O → *OH + H+ + e-

ORR is the reverse reaction of HER. (T/F)

False

Which of the following heterojunction type is the most efficient in suppressing the recombination of photo-generated electron and hole pairs in semiconducting photocatalysts? Type I. Type II. Type III. None of the above.

Type II

Which of the following biomass thermal conversion process does not require oxygen? A. Combustion. B. Gasification. C. Pyrolysis. D. None of the others.

C. Pyrolysis.

A good HER catalyst should have very strong hydrogen absorption property. (T/F)

False

Excessive oxygen is needed in the combustion of biomass. T/F

True

Which of the following material can NOT be used for hydrogen storage? A. MOF. B. Carbon nanotubes. C. Glass microspheres. D. LiCoO2

D. LiCoO2

Which of the following material is NOT used for CO2 adsorption or separation? A. Zeolite. B. Limestone. C. MOF. D. YSZ.

D. YSZ.

In an electrocatalytic water splitting reaction, OER is kinetically faster than HER. (T/F)

False

Biofuels produced from leaves belong to _____. A. the first generation biofuel B. the second generation biofuel C. the third generation biofuel D. the fourth generation biofuel

B. the second generation biofuel

To achieve photocatalytic hydrogen evolution from water (pH=0), the conduction band minimum of a semiconductor photocatalyst should be ____. A. 1.0 V vs. NHE B. 1.23 V vs. NHE C. positive vs. NHE D. negative vs. NHE

D. negative vs. NHE

For photocatalytic full water splitting, which of the following statement is true? CBM: conduction band minimum; VBM: valence band maximum. a. The CBM should be more positive than the HER potential and the VBM should be more negative than the OER potential. b. The CBM should be more negative than the HER potential and the VBM should be more positive than the OER potential. c. The CBM should be more positive than the HER potential and the VBM should be more positive than the OER potential. d. The CBM should be more negative than the HER potential and the VBM should be more negative than the OER potential.

b. The CBM should be more negative than the HER potential and the VBM should be more positive than the OER potential.

Biomass thermal conversion is generally considered to produce a net increase of CO2. (T/F)

False

assignment Flashcards

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