This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Application of Carbon Nanotubes”.
1. What is the advantage of using SWCNTs in monitors?
a) Residual gases are ionized
b) Electron emitter is bombarded with ions
c) Resistance to emission of coloured light on thin panels
d) Stable and inert than metallic electron inputs
View Answer
Explanation: A commercial application of CNTs is in flat panel displays. SWCNTs are inert and quite stable in comparison to the common sources of electron input (metallic or inorganic) to excite the emission of coloured light on the thin panels. The pixels of CNTs can be switched to excite green, red or blue phosphors and thus are able to form a full – coloured image. CNT displays have very high brightness and durability. Therefore, they are preferred to be used in flat monitors.
2. CNTs are used as coatings for gaskets and enclosures.
a) True
b) False
View Answer
Explanation: CNTs are added as additives to plastics owing to their high aspect ratio that increases strength. Furthermore, their natural tendency to develop ropes offer inherently very long conductive pathways even at ultra-low loadings. These properties have found its use as coatings for gaskets and enclosures.
3. Label the marked parts of a CNT-FET
a) (i) Insulating layer (Silicon dioxide); (ii) Carbon nanotube
b) (iii) Silicon substrate; (iv) Insulating layer (Silicon dioxide)
c) (i) Carbon nanotube; (iii) Doped silicon (gate)
d) (ii) Doped silicon (gate); (iv) Silicon substrate
View Answer
Explanation: In the given diagram of a CNT-FET, the marked parts are labeled as (i) carbon nanotube, (ii) Insulating layer ( silicon dioxide), (iii) Doped silicon (gate), (iv) Silicon substrate. CNT-FET can be formed by draping the nanotube in between the source and drain contacts. A highly doped silicon layer placed beneath the insulated layer can act as the gate contact of the FET.
4. What are carbon nanotube interconnects?
a) Structures connecting electrons
b) Structures connecting seamless cylinders
c) Structures connecting CNT walls
d) Structures connecting Integrated circuits
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Explanation: In integrated circuits (ICs), interconnects are the structures that are able to join two or more circuit elements together electrically. Recently, it has been proposed to make use of CNTs in the interconnects. Metallic CNTs can someday possibly replace copper interconnects.
5. Which of the following is not an advantage of X-ray equipments with SWCNTs as cathodes?
a) Larger equipments and machineries
b) Operative at room temperature
c) Greatly efficient
d) Very cost – effective
View Answer
Explanation: SWCNTs can be used in X-ray equipments in place of the metal filaments owing to several advantageous features. In case of X-ray equipments making use of metal filaments, high temperatures need to be supplied before applying an electric field. This is however not the case for CNTs which can operate at room temperature. The machineries used can be quite small, portable, economical and hence more efficient.
6. CNTs are absolutely non-toxic in nature.
a) True
b) False
View Answer
Explanation: CNTs have been established to be toxic to human body. They are harmful to liver and lungs since they accumulate in the reticuloendothelial system. Further, long – term exposure can induce some irreversible malignant transformations and change the pathways of lung epithelial cells that are related to cancer.
7. Which of the following is the most promising field of CNT application?
a) Space elevators
b) Solar cells
c) Stab proof
d) Thermal camouflage aircraft
View Answer
Explanation: The most promising application of CNT is solar cells. Researchers have developed solar cells that make use of CNT. Unlike typical solar cells that have peak efficiency at 90°, these cells have two peaks at 45°. They operate with high efficiency throughout the day.
8. How are SWCNTs useful in artificial muscles?
a) Do not replace existing polymeric gels
b) Light in weight
c) Reduce the conductivity
d) Slow response
View Answer
Explanation: Artificial muscles are devices or materials that mimic and perform functions of a natural muscle upon encountering an external stimulus. CNT sheets can be used as electrodes for actuators due to their light weight, good electrical conductivity and great mechanical properties.
9. How can CNTs be helpful in structural reinforcement?
a) Increase the weight
b) Reduce the flexibility
c) Lower the aspect ratio
d) Enhance the flexural strength
View Answer
Explanation: The great mechanical properties such as high tensile strength and large length: diameter ratios of CNT manifest its immense potential to be used in structural reinforcements. The CNT reinforced composites can have high flexural and compressive strengths combined with smaller strain and higher density.
10. Which of this company has developed a flat – panel display with CNTs?
a) Lenovo
b) Samsung
c) Volvo
d) Bee chems
View Answer
Explanation: Samsung in Korea has developed a flat – panel display using the electron emission of carbon nanotubes. They fabricated a field emission display with MWCNT strips on the cathode and phosphor-coated ITO strips on the anode.
11. Why are CNTs being used as additives in polymers?
a) They decrease the interfacial polarization phenomenon
b) They help in increasing the electrical conductivity
c) They reduce the shielding effectiveness
d) They hamper the strength
View Answer
Explanation: CNTs can be introduced into host polymeric matrices inorder to enhance the electrical conductivity as well as real and imaginary-permittivity values. They are also responsible for increasing strength, number of conducting links and interfacial polarization phenomenon that lead to the improvement of shielding effect.
12. CNT has not yet being used in the production of which of the following?
a) Paper batteries
b) Li-ion batteries
c) Wall clocks batteries
d) Electric vehicle batteries
View Answer
Explanation: A wall-clock battery has not yet been developed that makes use of CNT as electrodes. However, scientists are developing paper batteries, Li-ion batteries and electric-vehicle batteries that use CNT in a pivotal role.
13. Find out the disadvantage of a carbon nanotube FET.
a) Fast degradation
b) High current handling
c) Low power dissipation
d) Good threshold voltage
View Answer
Explanation: CNTs have high conductivity that provides it with high current handling and low power dissipation. They do not suffer from electromigration effects under high-current drive owing to their covalent bonds. Also, they have better threshold voltage. However, CNTs tends to degrade very fast when exposed to air.
14. Identify one property that does not account for the use of CNTs in super-capacitors.
a) Superior electrical conductivity
b) Thermal stability
c) Inaccessible surface area
d) Good mechanical properties
View Answer
Explanation: CNTs have superior electrical properties, great mechanical strength and thermal stability. They also possess readily accessible surface area and unique pore structure. These characteristics make CNTs eligible for super-capacitor electrode applications.
15. In what way is the addition of CNTs to ceramics useful?
a) Provide a wear or friction free surface
b) Lower the fracture resistance
c) Decrease the thermal conductivity
d) Enhance the brittleness compared to monolithic ceramic materials
View Answer
Explanation: CNTs when added to ceramic matrix can enhance their thermal as well as electrical conductivity along with fracture resistance. They can also provide wear and friction free surface. They have found their applications in load bearing structural parts providing them great strength. CNT-ceramic composites exhibit less brittleness compared to monolithic ceramic materials.
Sanfoundry Global Education & Learning Series – Nanotechnology.
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