Seminar On

Nanomaterials and MetamaterialsBy

Deepak Raj (2016JIT2116)

Industrial Tribology, Machine Dynamics and Maintenance Engineering Centre (ITMMEC)

IIT Delhi

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Nanomaterials

• Nanomaterial are characterized by at least one dimension in the Nanometer range.

• Carbon is the key element in Nanotechnology and so sometime nanotechnology also called carbon Nanotechnology.

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Two principal factors cause the properties of nanomaterials to differ significantly from Bulk materials: 1. Increased relative surface area2. Quantum effects.

These factors can change or enhance properties such as reactivity, strength and electrical characteristics.

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Surface Effects • As a particle decreases in size, a greater

proportion of atoms are found at the surface compared to those inside. For example, a particle of

• Size-30 nm-> 5% of its atoms on its surface• Size-10 nm->20% of its atoms on its surface• Size-3 nm-> 50% of its atoms on its surface• Nanoparticals are more reactive than large

particles (Catalyst)

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Quantum EffectsQuantum confinementThe quantum confinement effect can be observed once the diameter of the particle is of the same magnitude as the wavelength of the electron Wave function.Quantum confinement is responsible for the increase of energy difference between energy states and band gap. A phenomenon tightly related with the optical and electronic properties of the materials.When materials are this small, their electronic and optical properties deviate substantially from those of bulk materials.(GOLD)

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Classification

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Graphene• Monolayer of 2-D lattice of SP2 bonded carbon

atoms• Bond Length approximately 0.14 nm• Produced by mechanical cleavage of Graphite• It is a gapless semiconductor• Very promising to make ballistic field effect transistor,

can be used for development of carbon transistor

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Carbon Nanotubes(CNT)• It is single sheet of graphite rolled into a tube,

both ends of which are capped with fullurene hemisphere.

• Length is much greater than diameter.• Extremely strong, stiff and relatively ductile.• These have relatively low density• So also termed as Ultimate fibre as extremely

promising as reinforcement.

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Quantum Dots• Quantum dots (QD) are very small particles, so

small that their optical and electronic properties differ from those of larger particles.

• Quantum dots are also sometimes referred to as artificial atoms.

• These are semiconductor nanocrystals.• It emits specific wavelength of electro

magnetic radiation depending on its size.

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Properties

Optical •Optical properties depends on quantum size

Electrical •Can store considerably more energy due to more surface area

Chemical •Higher surface to volume ratio responsible for higher reactivity

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Metamaterials

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What is a Metamaterial?A periodic material that derives its properties from its structure rather than its components.

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• A metamaterial ( Greek word μετά meta, meaning "beyond") is a material engineered to have a property that is not found in nature.

• The materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence.

• Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures.

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Their precise shape, geometry, size, orientation and arrangement gives them their smart properties capable of manipulating electromagnetic waves: by blocking, absorbing, enhancing, or bending waves, to achieve benefits that go beyond what is possible with conventional materials.• Can achieve negative index of refraction, zero

index of refraction, magnetism at optical frequencies, etc.

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Classification

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Example: How to achieve negative index of refraction

• negative refraction can be achieved when both µr and εr are negative

negative µr and εr occur in nature, but not simultaneously

silver, gold, and aluminum display negative εr at optical frequencies

-

rrn

1/2 /2 /2( )( ) ( )( ) 1j j j j jr r e e e e e

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How Metamaterials trick light?

Lights get bend which is collective and combined effect of all the water molecules that is interacting with light and so it bends.

Fig: Positive Index of Refraction

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Fig: Negative Index of Refraction

Light gets bend otherway. This is because it is a negative index metamaterials.

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Invisibility

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When a light beam heat or excite a materials, Its surface reflects and scatters around all the wave that is interacting with it. And our eyes are able to pickup a portion of scattering wave and so we are able to see it.

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• If we can avoid all the interaction between light and object or cancel all the scattered wave , the object can become invisible.

• We want to eliminate whole scattered wave around the object including the shadow on the back of the object so to make object completely undetectable.

• Possible by designing Metamaterials that would scatter a form of negative light opposite to that of object then by balancing the positive light scattered from the object and negative light scattered from Metamaterials , It may be able to cancel the whole scattered wave and the light gets through the object without being detected.

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Application of Metamaterials

Bend light to effectively create an invisibility cloak

Construct satellite trackers that never need to move. Similar technology could serve as portable, energy-efficient satellite communication units for soldiers on the battlefield.

Enable ultra-fast data processing. Metamaterials could also reduce the size of chips so that they'd be tiny and speedy.

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Beam broadband connections to planes, trains, ships and cars. Imagine having internet access, well, everywhere.

Create a camera that uses compressed microwave images without a lens or moving parts. This could replace the bulky gateways currently in use at airports.

Become the building blocks for a high-speed fiber-optic telecommunications network

Contribute to making efficient solar cells less bulky

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Questions

1. What factors enhance the properties of Nanomaterials?

2. Classify nanomaterial citing example of each.3. Write Short notes on Graphene, CNT and

Quantum Dots.4. Mathematically show how negative refractive

index achieved in Metamaterials?5. Illustrate the concept of Invisibility?6. What are the application of Metamaterials?

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