بسم هللا الرحمن الرحيم

صدق هللا العظيم

SYNTHESIS OF NANOMATERIALS

Mohamed Mohamed Esmat

Demonstrator

Faculty of postgraduate studies for advanced sciences

Materials science and nanotechnology department

Top -Down

Nanoparticles

Bottom-Up

Characteristics of Nano particles that

should posses by any fabrication

technique:

Getting a small size is not the only requirement.

It should have:

Identical size of all particles

Identical shape or morphology.

Identical chemical composition and crystal structure

Individually dispersed or mono dispersed i.e., no agglomeration.

Characteristics of Nano particles that

should posses by any fabrication

technique:

1- Top down approach

Objectives of the milling process include;

1. particle size reduction

2.particle shape changes

Ball milling

The most effective ratio for the ball to powder masses

is 10 to 1.

Factors affect on ball milling process

• Milling Time

• Balls Number

• Balls weight

• Container volume

• Number of rounds per min.

Mechano-chemical activation

of copper ferrite

Time of milling, hrs.

-20 0 20 40 60 80 100 120

Cry

sta

llin

e s

ize

, n

m.

0

50

100

150

200

250

220 nm CuFe2O4 Ball millingTime, hrs. 10 20 40 100

Size, nm 143 89 50 99

200 nm

2. Bottom-up approach

Preparation from solids

Wt. = M * Mol. Wt. * V(L)

Preparation from liquids

M = (10 P * d ) / Mol. wt

• Used to prepare nanoparticles of metal

oxides.

• This process involves dissolving a salt

precursor usually a chloride, oxychloride, or

nitrate,

• Such as AlCl3 to make Al2O3

• Useful in preparing composites of different

oxides by co-precipitation of the corresponding

hydroxides in the same solution

Size and shape control?????

• The method is based on the ability of water and aqueous

solutions to dilute (at high temperature (500°C) and

pressure) substances practically insoluble under normal

conditions: some oxides, silicates, sulphides.

• They easily controlled the size of the NPs from 6 to 170 nm

by adjusting the experimental parameters such as

• The reaction duration,

• The initial pH ,and

• Initial concentration of the reactants.

Hydrothermal method

The main drawbacks

• The slow reaction kinetics.

• The high cost of equipment.

Advantages

• The ability to synthesis crystals of substances which are unstable

near the melting point.

• Application of powerful ultrasound radiation (20 KHz–10

MHz).

• Creation,

• Growth, and

• Collapse

What is the main drawback of this method????

Ultrasonication

Instrument

Microwaves are electromagnetic waves

Microwave

Instrument

• Microwaves will not affect the structure

of molecules.

• The effect of microwave is purely

kinetic.

• Fast

Conductive heating

Traditionally, chemical synthesis has been

achieved through conductive with external heat

source.

Slow (can take hours).

Insufficient for transferring energy into the system

because it depends on the thermal conductivity.

Uncontrolled.

Inhomogeneous temperature profiles within the

reaction flask.

Conventional heating

Microwave heating

Conversion of the electromagnetic

radiation into heat energy

• Heating is caused by:

1. Dipole rotation

The interaction of the permanent dipole moment of

the molecule with the high frequency

electromagnetic radiation.

Any polar species (solvent and/or substrate) that are

present will encounter this mechanism of energy

transfer.

Microwave heating

2. Ionic conduction:

It results if there are free ions or

ionic species (dissolved (dissociated)

charged particles) present in the

substance being heated.

Microwave heating

Advantages

• Reaction rate acceleration

• Higher yields

• Easy handling

• Environmentally friendly

• Control morphology and size

• Save energy and time

• large-scale industrial production of high-quality advanced

nanomaterials

• Leads to a particle sizes in the range of 15–35 nm because of the

shorter synthesis time and highly focused local heating.

Factors

Microwave heating is believed to be more dependent

on:

• The molecular properties

• The reaction conditions

• PH

• Temperature (power)

• Concentration

• Time

Sputtering

Instrument

Mohamed Esmat