This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Nanocomposites”.
1. Identify a method exclusively meant for the production of silicon nanocomposites.
a) Liquid infiltration
b) Electroless coating
c) Polymer precursor process
d) Hot pressing
View Answer
Explanation: Polymer precursor process is used exclusively for the production of silicon nanocomposites. It involves mixing of a Si-polymeric precursor with the matrix material followed by its pyrolysis using an oven. This generates the reinforcing materials, that have better dispersion.
2. Match the following.
I. RSP with ultrasonics (i) Homogeneous mixing and uniform distribution II. Electroless coating (ii) Mechanical mixing of CNTs with pre-polymer melt III. High energy ball milling (iii) Mixing and improving wettability between matrix and the reinforcements IV. Melt mixing (iv) Reduction of SnCl2 & SbCl3 by KBH4
a) I – (iii); II – (iv); III – (i); IV – (ii)
b) I – (i); II – (iii); III – (iv); IV – (ii)
c) I – (iv); II – (ii); III – (iii); IV – (i)
d) I – (ii); II – (i); III – (iv); IV – (iii)
View Answer
Explanation: RSP uses ultrasonics for mixing and improving wettability between the matrix and reinforcements. High energy ball milling involves homogeneous mixing and uniform distribution of the reinforcing materials. Melt mixing brings about the mechanical mixing of CNTs with pre-polymer melt followed by compression moulding. Electroless coating employs reduction of SnCl2 and SbCl3 precursors by KBH4 in the presence of CNTs.
3. Nanoscale dispersion is a process employed for the synthesis of polymer based nanocomposite systems.
a) True
b) False
View Answer
Explanation: Nanoscale dispersion technique is used for the production of metal-CNT nanocomposite systems. It is preceded by the preparation of the precursor of MWCNT, using natural rubber and ethyl propylene. The CNTs produced are mixed with aluminium powder and rolled into sheets by compression moulding at 353K. The precursors are then placed on an Al plate and heated in N2 atmosphere for almost an hour. This is then cooled down to form the final product.
4. Which among the following is not an advantage of the Sol-gel process of ceramic nanocomposite production?
a) Greater shrinkage
b) Rigorous stoichiometry control
c) High chemical homogeneity
d) Versatile method
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Explanation: Sol gel process employed for the production of ceramic nanocomposites is quite advantageous. It is a simple, versatile low processing temperature technique which forms products of high purity. It also has high chemical homogeneity and rigorous stoichiometrical control over its materials. However, the disadvantages are greater shrinkage and lower amounts of voids in the product compared to the mixing method.
5. What is the correct procedure for the fabrication of devitrified nanocomposite steel?
a) Quenching the metallic glass ➔ Devitrifying the glass precursor ➔ Heat treatment above its crystallization temperature ➔ Crystalline multi-phase microstructures
b) Heat treatment above its crystallization temperature ➔ Quenching the metallic glass ➔ Devitrifying the glass precursor ➔ Crystalline multi-phase microstructures
c) Crystalline multi-phase microstructures ➔ Heat treatment above its crystallization temperature ➔ Quenching the metallic glass ➔ Devitrifying the glass precursor
d) Devitrifying the glass precursor ➔ Crystalline multi-phase microstructures ➔ Heat treatment above its crystallization temperature ➔ Quenching the metallic glass
View Answer
Explanation: Devitrified nanocomposite steel is an iron-based nanocomposite material obtained by quenching metallic glass produced from Fe-based alloy. This is followed by the devitrification of the glass precursor through heat treatment above its crystalline temperature. The resulting product exhibited a crystalline multi-phase microstructure.
6. Choose the correct statement from the following.
a) Electroless coating occurs at 873K and 200 torr
b) Sol-gel method can only be used to synthesize polymer-based nanocomposites
c) Intercalation from solution cannot be used for layered reinforcing material
d) In-situ polymerization makes use of infrasonics for dispersion in epoxy system
View Answer
Explanation: Electroless coating is used for the synthesis of metal-CNT nanocomposite systems. It involves thermal treatment under the conditions 873K, 200 torr in the presence of 10% H2 or N2 flow gas. Intercalation from solution is a method employed for layered reinforcing material in which the polymer may intercalate. In situ polymerization uses ultrasonics for dispersion in epoxy systems.
7. Find out the advantage of powder process used for the synthesis of ceramic nanocomposites.
a) Simple and easy
b) Causes agglomeration
c) High temperature process
d) Secondary phase formation
View Answer
Explanation: Conventional powder process is a simple method for the production of ceramic nanocomposites. However, there are more cons to this process than pros. These are low formation rate, poor phase dispersion, agglomeration, requirement of high temperature, and formation of secondary phases in the product.
8. What is the correct sequence of steps taking place in the fabrication of Fe/MgO nanocomposite system using spray pyrolysis?
a) Vaporization of droplets in the chamber ➔ Inorganic precursors dissolved in solvent ➔ Selective reduction of metal oxides ➔ Formation of mist using ultrasonic atomiser ➔ Carrying mist into pre-heated chamber
b) Inorganic precursors dissolved in solvent ➔ Formation of mist using ultrasonic atomiser ➔ Carrying mist into pre-heated chamber ➔ Vaporisation of droplets in the chamber ➔ Selective reduction of metal oxides
c) Carrying mist into pre-heated chamber ➔ Vaporization of droplets in the chamber ➔ Inorganic precursors dissolved in solvent ➔ Selective reduction of metal oxides ➔ Formation of mist using ultrasonic atomiser
d) Selective reduction of metal oxides ➔ Carrying mist into pre-heated chamber ➔ Formation of mist using ultrasonic atomiser ➔ Vaporization of droplets in the chamber ➔ Inorganic precursors dissolved in solvent
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Explanation: Spray pyrolysis begins with the dissolution of the inorganic precursors in a suitable solvent. This generates a mist from the mixture when an ultrasonic atomiser is used. The mist is then carried to a preheated chamber using a carrier gas. The mist is then vaporized and trapped with a filter promoting their decomposition to produce respective oxide materials. Reducing agents conduct selective reduction of the metal oxides to produce respective metallic nanocomposites.
9. Which of the given method involves sputtering of different components to produce metal based nanocomposite systems?
a) Liquid infiltration
b) Direct mixing
c) In-situ polymerization
d) Physical vapour deposition
View Answer
Explanation: PVD or Physical vapour deposition is a metal based nanocomposite system. It involves sputtering/evaporation of different components to form vapour-phase. This is supersaturated in an inert atmosphere to promote the condensation of metal nanoparticles. Ultimately, the consolidation of nanocomposites is carried out by thermal treatment in an inert atmosphere.
10. Sol-gel method remains unaffected by parameters such as temperature or pH.
a) True
b) False
View Answer
Explanation: Sol-gel process used for the synthesis of ceramic nanocomposites is affected by a large variety of parameters. These are the types of solvents used, timing, precursor used, pH of solution, water to metal ratio etc. These factors regulate the structural and chemical properties of the final reinforcing materials.
More MCQs on Nanocomposites:
- Nanocomposites MCQ (Set 2)
- Nanocomposites MCQ (Set 3)
- Nanocomposites MCQ (Set 4)
- Nanocomposites MCQ (Set 5)
Sanfoundry Global Education & Learning Series – Nanotechnology.
To practice all areas of Nanotechnology, here is complete set of 1000+ Multiple Choice Questions and Answers.
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