Nanotechnology Questions and Answers – Application of Carbon Nanotubes – Set 2

This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Application of Carbon Nanotubes – Set 2”.

1. Select the correct statement from the given options.
a) CNT-FET without doping acts as an n-channel device
b) Scottky contacts are interfaces between CNT and the source and drain
c) Potential barrier height in CNT-FET can be reduced by decreasing tube diameter
d) n-channel CNT-FET can be converted to p-channel device after oxygen exposure and annealing
View Answer

Answer: b
Explanation: In a CNT-FET without any intentional doping the CNT acts as a hole conductor forming a p-channel device. The interfaces between the CNT and the source and drain are Scottky contacts. This potential barrier can be reduced in height by increasing the tube diameter which decreases its band gap and effective mass. A p-channel CNT-FET can be converted to an n-channel device upon oxygen exposure and annealing.

2. Which company discovered Vantablack?
a) Abeam Technologies
b) Icon Analytic Equipment
c) Surrey Nanosystems
d) Nanosniff Technologies
View Answer

Answer: c
Explanation: Vantablack is a material created by the researchers of Surrey Nanosystems in 2014 in the United Kingdom. It is the darkest substance known to mankind as it can absorb upto 99.96% of visible light.

3. Which among the following materials can be used for EMI/RFI shielding?
a) CNT-plastic composites
b) CNT-metal composites
c) CNT-ceramic composites
d) CNT-gaseous composites
View Answer

Answer: a
Explanation: EMI stands for electromagnetic interference and when dealing with radio frequency, it is considered as radio-frequency interference. CNT-plastic composites can provide light weight shielding material for electromagnetic radiation. It can serve a great purpose in the military by protecting the computers and electronic devices from electromagnetic pulses. These devices are used to develop a highly digitalized battlefield for command, control and communication.

4. Carbon-nanotubes have the capability of storing which of the following gases.
a) Oxygen
b) Peroxides
c) Hydrogen
d) Nitrogen
View Answer

Answer: c
Explanation: CNTs are able to store hydrogen in them that presents a viable alternative to energy storing cells. There is a high chance of using CNTs in fuel cells as they need a source of hydrogen. There is an estimation that nearly 6.5% hydrogen by weight has to be stored in CNTs for their use in fuels cells. Research has revealed that CNTs can at present hold only 4% hydrogen by weight.

5. Which among the following is not a characteristic of a CNT gas sensor?
a) Lower power consumption
b) Enhanced size
c) Higher sensitivity
d) Lower working temperature
View Answer

Answer: b
Explanation: CNTs can be used as gas sensors. This is because of their faster response, lower power consumption and higher sensitivity. These can operate at room temperature without much heating so the central element can be increased in length, while even extending the useful life of the sensor battery.

6. Choose the incorrect statement with respect to the uses of DWCNTs.
a) Used for potable water purification
b) Used as gas sensor for fast response and lower power consumption
c) Used in making parts of aircrafts
d) Used in preparation of conductive inks
View Answer

Answer: a
Explanation: In the recent years DWCNTs have widely found their applications in various fields. It is used as gas sensor for faster response, lower power consumption, higher sensitivity, smaller size and lower working temperature. It is used in making parts of aircrafts owing to their great mechanical properties. They have also been applied for the preparation of conductive inks.

7. Identify the material that can be used for coating turbine blades.
a) Organic solvents
b) CNT-polymer composites
c) Endohedral fullerenes
d) CNT-ceramic composites.
View Answer

Answer: d
Explanation: Turbine blades are coated with thermal barrier coatings (TBCS) that are advanced ceramic coatings. Since, ceramic materials are hard heat and chemical resistant they are used for such coatings. However, they are brittle in nature. Use of CNT-ceramic nano composites can reduce this brittleness and provide resistance to fracture and cracking under stress.

8. What is the mistake in the given diagram for an electrochemical cell used to inject hydrogen into CNTs?

a) Negative electrode
b) Voltage supply
c) Positive electrode
d) Electrolyte
View Answer

Answer: d
Explanation: Hydrogen can be injected into CNTs by the use of electro-chemical cell. SWCNTs, in the form of paper, are used as negative electrodes in a potassium hydroxide (KOH) electrolyte solution. The positive electrode used is made of Ni(OH)2.

9. Why are CNTs considered as catalyst supports?
a) Catalyze the uncontrolled reactions
b) Unable to attach chemical species
c) Possess high surface area
d) Do not undergo chemical functionalization
View Answer

Answer: c
Explanation: CNTs serve as catalysts for certain chemical reactions. They possess extremely high surface area combined with the ability to undergo functionalization that offers a prospect for unique catalyst support. For e.g.:- Ruthenium (Ru) metals attached to nested nanotubes have exhibited strong catalytic effect in the hydrogenation reaction of cinnamaldehyde.

10. Why are lithium batteries using CNTs more efficient than normal lithium batteries using graphite?
a) Store a lithium ion for every five carbon atoms
b) Store a lithium ion for every nine carbon atoms
c) Store a lithium ion for every three carbon atoms
d) Store a lithium ion for every seven carbon atoms
View Answer

Answer: c
Explanation: Lithium batteries generally make use of graphite electrodes in its system. If these are replaced by carbon nanotube electrodes, these can last even longer. The use of SWCNT as electrodes can also double the storage capacity. Several studies have shown that they are capable of storing a lithium ion for every 3 C-atoms compared to graphite that stores one for every six carbon atoms.

11. Identify a material that can be used in thermal camouflage.
a) Blue vitriol
b) Cream of tartar
c) Maya Blue
d) Vantablack
View Answer

Answer: d
Explanation: Vantablack is a compound of vertically aligned nanotube arrays. It is the darkest material known to mankind. It increases absorption of heat in materials as it absorbs 99.965% of visible light. Since our eyes need reflected light to see materials we are looking at, Vantablack is perceived as a black hole. It has thus found its use in the military for thermal camouflage.

12. DWCNTs are used in tennis rackets.
a) True
b) False
View Answer

Answer: a
Explanation: DWCNTs are used as reinforcements for their great strength, light weight and high – performance composites. These are lately being used to enhance sporting good like tennis rackets, basketball balls and bicycle frames.

Sanfoundry Global Education & Learning Series – Nanotechnology.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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