Engineering PhysicsChapter 8

Nanophysics

Kazim Marfatiya

Mihir Prajapati

Harsh Mehta

Presented By:

Government Engineering College, Modasa

Contents Nanomaterials and Nanotechnology

• Aspects of Nanotechnology• Approaches in Nanotechnology• Nanotechnology: Size and Scale

Unusual Properties of Nanomaterials Disadvantages of Nanomaterials

Nanotechnology• the branch of technology that deals with dimensions and tolerances of

less than 100 nanometers, especially the manipulation of individual atoms and molecules

• Nanotechnology is engineering at the molecular (groups of atoms) level

• It is the collective term for a range of technologies, techniques and processes that involve the manipulation of matter at the smallest scale (from 1 to 100 nm2)

Aspects of nanotechnology

DirectApplication of novel,

Nano engineered artifacts

Ex : Electronic & photonic circuits

Indirect Progressive

miniaturization of existing

technologiesEx : Nano bots,

cosmetics

ConceptualAll materials & processes are

considered from a molecular viewpoint

Ex : Universal manufacturing

model

Creating Nano-scale materials by physically or chemically breaking

down larger materials

Assembling Nano materials atom-by-atom or molecule-by

molecule (self assembling)

Approaches in nanotechnology

Top-down Approach Bottom-up Approach

Nanotechnology: Size and Scale

Application Of Nanotechnology

Agrochemical Ex: Nanoparticles in

pesticides

ConvergenceNano-Geo-(Bio)-Info

technology

In food industr

y

SensingEx: Detect

chemicals or food borne pathogen

SafetyPackaging

Ex: Prevent or respond to spoilage

Nano powders - building blocks of Nano materials (particles less than 100 nm in size)

Nanoparticles of gold for

new catalysts

The scale of

Nano powders

Nano materials

Porous metallic ‘Nano cubes’

store large amounts of H2

Properties Of Nano materials

Optical Property

• Due to surface Plasmon resonance• Due to the increased energy level spacing

Mechanical Property

• Dislocation-free or perfectness as grain diameter deceases from 50-100nm

• Some pores or flaw originated from preparation method

Elastic Property

For grain size<5nm: decreasing E due to number of atoms associated grain boundaries becomes very large

Hardness and strength

• Increase with (grain diameter)-1/2 (Hall- Patch equation)• since grain boundaries: barrier against dislocation movement• Some NC materials have showed deviation from H-P equation…

Ductility and toughness

• Increase in coarse grain size materials(d>1um), toughness and ductility increases

• NC materials(d<30nm): brittle

Superplastic behavior

• elongation(tensile deformation) of 100% to >1000% without necking or fracture

• Some NC: super plasticity transition temperature is lowered and strain rate increased with the decrease in d, usually for T>0.5Tm

Some Other Properties of Nanomaterial

High Strength, Hardness, Formability and toughness

More Brittle

Super Plasticity

Magnetic moment can be increased

Optical Density can be varied with the diameter

Melting point gets reduced on reducing the grain size

The Magnetization and coercivity are higher

Disadvantages of Nanomaterials

Impurities

Since nanomaterial are highly reactive ,they inherently interact with impurities as well. In addition, encapsulation of nanoparticles become necessary whey they are synthesized in a solution.

It is extremely hard to retain the size of nanoparticles once they are synthesized in a solution.Hence, the nanomaterial have to be encapsulated in a bigger and stable molecule/material. Hence free nanoparticles are hard to be utilized in isolation, and they have to be interacted use via secondary means of exposure.

Difficulty in synthesis, isolation and application

Instability of particles

Retaining the active metal nanoparticles is highly challenging , as the kinetics associated with nanomaterials is rapid.

Effect On Human Body

Nanoparticles are small enough to be absorbed by the skin and cause irritation and have indicated to be carcinogenic.Breathing in any fine or tiny solid particles can cause irritation in the lungs and can cause lung cancer.Example:- coal workers, quarry workers etc.

Some more disadvantages of nanomaterials..

Chemicals in the form of tiny nanoparticles have been shown to spread throughout a crop plant and affect

growth and soil fertility

Nanosilver particles kill bacteria. But they

kill good non-bacterial cells or good bacteria if it is inhaled

or ingested.

No hard and fast safe disposal policies

evolved

Nanomaterials are more costly to

produce compared to more traditional bulk

materials

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