Engineering Physics Multiple Choice Questions on “Nano Phase Materials”.
1. In which of the following the atoms do not move from each other?
a) Shape memory alloys
b) Nano materials
c) Dielectrics
d) Static materials
Answer: b
Clarification: There exists a special type of material in which the atoms do not move away from each other and its size will be in the order of 1-100nanometers. These new materials are called nano-materials.
2. Which of the following uses radio frequency to produce nano-particles?
a) Plasma arching
b) Chemical vapour deposition
c) Sol-gel technique
d) Electro deposition
Answer: a
Clarification: Nano particles are produced by generating plasma using Radio frequency heating coils in plasma arching method. It consists of an evacuated chamber, wounded by high voltage RF coils.
3. Which of the following methods can be used to produce nano-powders of oxides?
a) Plasma arching
b) Sol-gel technique
c) Chemical vapour deposition
d) Mechanical crushing
Answer: c
Clarification: Chemical vapour deposition is used to prepare nano-powder. In this technique, initially, the material is heated to form a gas i=and is allowed to deposit on a solid surface under vacuum condition, which forms nano-powders on the surface of the solid.
4. Which of the following is used to make both nano-particles and nano-powders?
a) Chemical vapour deposition
b) Sol-gel technique
c) Plasma arching
d) Electro deposition
Answer: b
Clarification: Sol-gel technique is based on the hydrolysis of liquid precursors and the formation of colloidal solutions. Only this method can be used for the preparation of nano-particles and nano-powders.
5. Which method can be used to prepare iron nitriles nano-crystals using ammonia gas?
a) Pulsed laser deposition
b) Sol-gel technique
c) Electro-deposition
d) Mechanical crushing
Answer: d
Clarification: Mechanical crushing is the method sued in the preparation of metal oxide nano crystals. In this method, small balls are allowed to rotate inside a drum and are made to fall on a solid with a high gravitational force that crushes the solid into nano-crystals. Thus iron nitriles nano-crystal can be made by using mechanical crushing.
6. Nano-particles exhibit super plastic behaviour.
a) True
b) False
Answer: a
Clarification: The hardness of nano-phase materials varies from material to material. This may be due to the phase transformation, stress relief, density and grain boundaries. Therefore nano-particles exhibit super plastic behaviour.
7. Which of the following is used to modify the optical properties of a material system?
a) Electricity
b) Magnetic field
c) Pressure
d) Light
Answer: d
Clarification: In nonlinear optics, the modification of the optical properties of a material system is made by light. This is because according to electro optic effects when the light is passed through a material it changes the properties of the medium.
8. Find the odd one out.
a) Frequency mixing
b) Second-harmonic generation
c) Optical mixing
d) Raman and Rayleigh scattering
Answer: a
Clarification: The rest of the mentioned effects exhibit Bire fingence. When light passes through a material the incident ray splits into two rays, one of the same wavelength and the other of a different wavelength. This phenomenon is called double refraction. It is observed in NLO materials. Whereas frequency mixing is a passive material.
9. Which of the following is used in electro optic modulators?
a) Lithium tantalite
b) Barium sodium niobate
c) Lithium niobate
d) Lithium sodium niobate
Answer: c
Clarification: When an ordinary light is passed through the lithium niobate crystal, it is converted into polarised extraordinary light. Hence it is used in electro optic modulator.