1. NANOMATERIALS FOR
ADVANCED APPLICATIONS
SHRIRAM INSTITUTE FOR INDUSTRIAL RESEARCH
19, UNIVERSITY ROAD, DELHI-110 007
Email : sridlhi@vsnl.com Website : www.shriraminstitute.org
Presented by :
Dr. R.K. KHANDAL
3. Classification of Materials (Type & Structure)
Composites
Ceramics
Polymeric
Crystalline
Polycrystalline
Amorphous
Metallic
Electronic
Biomaterials
Nanomaterials
Nanomaterials include all classes of materials at the nanoscale
Nanomaterials are categorized as 0-D (nanoparticles),1-D
(nanowires, nanotubes, nanorods), 2-D (nanofilms,
nanocoatings), 3-D (bulk)
4. Properties of Materials : Critical Factors (Bulk Vs Nano)
DefectsDefects
+
Mechanical
Optical
Thermal
Magnetic
At the nanoscale, interactions with heat ,light, stress, electrical
field & magnetic field give rise to interesting & novel properties
A thorough understanding of the nature of interactions at the
bulk & nano levels are essential for designing nanomaterials
InternalInternal
StructureStructure
Bulk
(Macro & micro)
Nano
SizeSize
ShapeShape
Surface area toSurface area to
Volume ratioVolume ratio
+
+
5. Nanomaterials:
Materials consisting of particles of the size of nanometer
Volume = Surface Area * Thickness
For a given volume:
Surface area Thickness
More atoms at surface than in the interior
Extraordinary activity
SCOPE: DEFINITION
6. SCOPE : DOMAIN
Keywords Domain
Particle size Distribution in the
continuous phase
Modification of surfaces Interfacial tension
Surfaces Interfaces
Rising volume fraction Homogeneity of phases
of dispersing phase
Domain of Nanotechnology: Multi-phase systems
Liquid : Liquid
Solid : Liquid
Surfaces and interfaces involving different phases
Gas : Liquid
Gas : Solid
7. Systems Process
Emulsion Macro Micro
Dispersion Coarse Fine
Solution Colloid
SCOPE: PROCESS
A process to create a continuous dispersed phase as fine as
possible for homogeneity with the dispersing phase
(Liquid / Liquid; Gas/Liquid)
(Solid / Liquid)
(Solid / Liquid; Liquid/Liquid)
Solubilization
8. SCOPE : DIMENSIONS
What Happens Dimensions
Particle size More from less
Surface area Enhanced coverage
Activity Novel products
Efficiency Improved performance
per unit mass
Maximum possible benefits from minimum possible inputs
Effecting changes through and at atomic scale
9. Nanomaterials: Features
Synergistic combinations of materials of different kinds & characteristics
is possible through nanotechnology
Coatings, Films
Surface modificationSize Reduction
10 nm
1 µm
1 cm
CompatibilityHuge interfaces
Solid Liquid
Homogeneous
solution
Inorganic
nanoparticles
in a liquid
media
+
10. Process of making Nanomaterials
Process steps Inputs
Macro
Micro
Nano
Challenges: Process Technology
Challenge: To have a process that can convert macro materials into
nanomaterials spontaneously & with minimum efforts
Energy
Bulk
Sugar cube
Nano
Dissolved sugar/salt
Bulk
Output
Salt
11. Multi-phase systems: Approach
Ability to design materials with tunable properties
In-situ way of production of nanomaterials leads to more
homogeneous matrix with higher loading of nanoparticles
Physical
Ball milling
Gas condensation
E-beam evaporation
Vapour deposition
Sputtering
Chemical
Microemulsion
Sol-gel
Chemical reduction
Ex-situ
In-situ
•Bulk production
•Reproducibility
•Stability
•Cost
• Single step
• Non-agglomeration
• Better Stability
• Interfacial interaction
Hydration
Hydrolysis
Solubilization
Chemical conversion
Precipitation
Concerns
Benefits
12. Synthesis of Nanomaterials: Ex-situ
TiO2 TiO2
-
-
-
-
-
-
TiO2
TiO2
-
-
-
-
-
-
MonomerPolymer
Surfactant
-
-Radical
Polymerization
10 nm
100 µm
Grinding
Latex Fe2O3-Particles
Fe2O3-Particles
Latex
bead
Pre-treatment
Polymerization
Copolymer
layer
Encapsulated particle
Amphiphilic
molecule
Monomer
Ex-situ synthesis of nanomaterials involves number of steps
Polymer encapsulated nanomaterials used for targeted delivery of drugs-
good example of ex-situ synthesis
13. Synthesis of Nanomaterials : In-situ
Metal salt + Monomer
Adopting in-situ approach of synthesizing nanomaterials reduces
number of steps involved and hence simple process !
Nanocomposite
1. Hydrolysis
2. Polymerization
14. Designing Nanomaterials : Approaches
Metal
Ceramic
Polymer
Matrix Reinforcing phase
Inorganic
Metals & inorganic
Metals
Examples
Carbides, borides,
nitrides, oxides, etc.
SiC, Zr, Fe, W, Mb,
Ni, Cu, Co, etc.
C nanotubes,
alumina, silica, etc.
Nanocomposites have tremendous scope in all areas of
science & technology.
15. 0 - D
1 - D
2 - D
Dimension
Thermal conductivity is more prominent in 1-D & 2-D nanomaterials
Thermal conductivity of C nanotubes (2-D nanomaterial) = 3000 Wm-1
K-1
;
Copper (bulk) = 400 Wm-1
K-1
Structure of Nanomaterials: Size and Shape
3 - D
Bulk
x , y , z
Nanocomposite
thick film
Rods
Tubes
Wires
d=100 nm
d 100 nm
Example
Nanoparticles
Nanofilms
Nanocoatings
Application
Bottle-neck
Waveguides
Components
for PC, Mobile
phones
x , y
x
Nil
Direction of
confinement
16. Unique Properties of Nanomaterials
Nano-sizeBulkProperties
Thermal • S / V
• Heat
transport
Small
Electrons
Large
Phonons
Unique properties at the nanoscale have led to the use of
nanomaterials in fields where conventional materials have limitations
Magnetic
Optical
• Super-
paramagnetism
Absent Prominent
• Absorption
• Emission
• Reflection
Bulk effects
Material
dependent
Surface Plasmon
effects
Size dependent
18. Transportation of Heat: Nanomaterials
Mechanism of heat travel : Electrons (metals) &
Phonons (non-metals)
λ Phonons ≈ L nanostructure; λ Phonons < L macrostructure
When size of the material is reduced to nanoscale,
quantum confinement occurs
Confinement at nanoscale occurs in 0-D (x, y, z
directions), 1-D (x,y directions), 2-D (x direction) and
3-D (bulk)
Quantum confinement effects ~ electron transport
mechanism of bulk materials
19. Pt bulk
Pt 28 nm
Pt 15 nm
λ0(W/mK)
T0 (K)
Properties of Nanomaterials : Thermal Conductivity
Separate 2 crystals of
same materials with
different orientations
(grain boundary)
Separate 2 crystals
of different materials
(multilayer structure;
different densities &
sound velocities)
Phonon scattering at
the interface
Interface
In nanosystems, there is presence of huge interfaces
Interfaces Thermal resistance
Phonon scattering Thermal conductivity
Films
21. Magnetism in Nanomaterials
Strong coupling
Critical particle size : below which material will be in
single domain; hence magnetism
If particle size is << critical diameter, loss of
magnetization occurs; super-paramagnetism
Interaction energy is effective at sizes less than critical
diameter but above super-paramagnetism
Critical diameter of Co = 70 nm & Fe = 15 nm
Small size of particles
Features Consequence
Dominance of exchange forces
Alignment of spins
22. Hc
D sp D crit
Single Domain Multi- Domain
Magnetic Properties
Coercive field of Ferromagnetic materials with particle size
Particle size < Dcrit Single domain Magnetization
Particle size <<< Dcrit Super-paramagnetism
24. Optical effects:Metamaterials
η =√µrεr
Most promising area of application : Metamaterials
Size, shape & composition of embedded nanoparticles influence
the interactions with light, heat ,sound & waves etc
1
2
1
2
+ve R.I.
-ve R.I.
Refractive Index
η =√µrεr
µr: Permeability to magnetic field
εr: Permeability to electric field
• µr, εr= -ve
• Induced phenomena
µr, εr= +ve
Natural phenomena
26. SOLAR SPECTRUM
Visible light
(43%)
X-rays Micro
wave
Radio
wave
Infra red
radiation
(54%)
UV
(3%)
Long Wavelength
1012
nm106
nm700 nm
Chemical changes :
Bond Dissociation
Bond Formation
Rearrangement
Electron
transfer
The energy of electron 1.23 eV ≅ λ1000nm; thus, energies
corresponding to λ < 1000nm can bring about chemical
changes.
The region from 200nm to 1000nm is most useful for
photochemical conversion.
Lux
400 nm 109
nm 1014
nmWavelength,λ
Short Wavelength
200 nm
27. SOLAR SELECTIVITY : MATERIALS RESPONSE
Frequency (Hz)
Visible
Infrared
Ultraviolet
X-rays
Cosmicrays
1081010
101210141016
1018
10201022
Radiofrequency
Gammarays
Microwave
High Potential for harnessing
the solar energy
Processes
involved Inner
electronic
transition
Outer
electronic
transition
Molecular
Vibrations
Molecular
rotations
vibrations
Electron
spin
resonance
Nuclear
magnetic
resonance
Change at atomic & molecular levels can become the
via media for harnessing solar energy.
Solar sensitive materials undergo region specific
transition Solar energy conversion
28. PHOTOCHEMICAL CONVERSION : MECHANISM
The Energy E of single photon is given by the Planck equation:- E=hν= hc/ λ
Sun light
.
…….. ...………………………………electron
Excitation photon
excited
state
Non-radiative
relaxation
Conduction
band
Valence
band
h+
e-
Band
gap
E=hν
Every photochemical conversion process requires as an initial steps
the absorption of photon energy and conversion into the internal
energy of the first excited state of the molecule of the material
φ =
Number of events
Number of photons absorbed
……………………
…………
30. The play of light on a butterfly’s wings has inspired designing of
novel photonic materials for solar cells, photovoltaics,
camouflaging, optical fibers and military applications
Invisibility cloak
Color play
Tailor-making of
refractive index
and dielectric
constant
Nanomaterials : Camouflaging
31. Nanomaterials: Photochemical Conversion
Advantages
Utilization of unabsorbed part of solar spectrum
Reduced heat dissipation
Quantum Dots
100 nm50 nm
Reactivity
10 nmSize (nm)
Nanotubes & nanowires
Mesoporous
32. MATERIALS FOR ENERGY CONVERSION :
SEMICONDUCTORS
Challenge is maneuver the band gap:make it sensitive to visible
light.
6.3 eV 3.15 eV 1.58 eV
U.V
200 nm 400 nm 800 nm
Visible
TiO2
ZnO
CdS
WO3
Band gap
Energy
EMS(λ)
TiO2 = 3.20 eV
ZnO = 3.35 eV
WO3 = 2.80 eV
CdS = 2.42 eV
Semiconductors are the most ideal and preferred materials.
33. Nanomaterials: Self-Cleaning
Hydrophobic Photocatalytic
Designing of materials with novel effects like hydrophobic,
hydrophilic, photocatalytic, etc. has made possible new
applications like self cleaning, coatings, etc.
Coating
Dirt run-
off
Light
Coating
Roll-off effect
34. Nano materials
101
Ti alloys
Brass
Mild steel
Al alloys
Copper
Lead
PE, PA
PP, ABS
PS, PET
PVC
Alumina
Zirconia
Glass
Concrete
Bricks
Metals Polymers Ceramics
Ideal Strength
High Strength Building MaterialsYieldStrength(σy)/Young’sModulus(E)
10-4
10-3
10-2
10-1
Bulk materials fall short of the ideal values in every aspect;
mechanical, optical, electronic, magnetic, thermal, etc.
Nanostructure, nanolayers & amorphous materials are strongest
37. Green Materials : Nanoengineered Concrete
Nanosilica
Precipitated
Silica
Silica
fume
Metakaolin
Finely ground
mineral additives
Portland cement
Fly ash
Aggregate fines
Natural sand
Coarse
aggregates
Nano engineered concrete
High strength/ high
performance concrete
Conventional
concrete
100
101
102 103
104
105
106
108
107
10-1
10-2
100
101
102
103
104
105
106
Particle size(nm)
SpecificSurfaceArea(Kg/m2
)
Nanoparticles allow better void filling & positive filler effects &
improved bond between pastes aggregates; nanosized additives
increase strength beyond what is attained with conventional materials
38. SRI’S EXPERIENCE
SRI has developed nanomaterials for :
Optical applications
Effluent treatment
39. 39393939393939
High Refractive Index Materials
The refractive index of low refractive index materials
increases from 1.49 to 1.66.
1.41
1.47
1.53
1.59
1.65
1.71
0 10 20 30 40 50 60 70 80 90 100
% of additive
Refractiveindex
40. 40404040
Refractive index increases with increase in percentage of
metal salt.
1.41
1.42
1.43
1.44
1.45
1.46
1.47
1.48
0 5 10 15 20 25 30
Metal salt (% by wt)
RefractiveIndex
Barium Hydroxide Lead Monoxide Lanthanum Oxide
High Refractive Index Acrylates
41. 414141414141
High Refractive Index Titanium Nanocomposites
In-situ formation of nanoparticles of Ti
The refractive index of the polymer increases from 1.45 to
1.53
1.44
1.46
1.48
1.5
1.52
1.54
0 2 4 6
% Ti
RefractiveIndex
42. Photocatalytic Material : Doped TiO2
XRD analysis confirms the doping of TiO2
Change in lattice parameter ‘a’ & ‘c’ of TiO2,confirms the
incorporation of Cd2+
in Ti4+
Influence TiO2 Doped TiO2 Doped TiO2
factor (In-situ) (External)
a/nm 3.0301 3.3184 3.3558
c/nm 9.5726 10.0136 11.2138
Intensity(a.u.)
Position (2 Theta)
20 30 40 50 60 70 80
External
In-Situ method
TiO2 market
procured
TiO2 (Reference)
43. 0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
200 300 400 500 600 700 800
Wavelength
Absorbance
MG A
B C
Semiconductors are used to prepare nanocomposites with
enhanced photocatalytic activity
Dye
Nanocomposites & dye degradation
44. Nanocomposites lead to complete degradation of dye
Useful for the treatment of dye effluents
91.29 92.30 94.49
37.29
86.61 87.19
0
20
40
60
80
100
A B C
Degradationrate(%)
Nano
Normal
Nanocomposites for dye degradation
