NANOMATERIALS FOR ADVANCED APPLICATIONS
SHRIRAM INSTITUTE FOR INDUSTRIAL RESEARCH19, UNIVERSITY ROAD, DELHI-110 007
Email : [email protected] Website : www.shriraminstitute.org
Presented by :Dr. R.K. KHANDAL
Outline Materials
Nanomaterials
Nanomaterials
Applications of Nanomaterials
Experiences of SRI
Properties
Domain Process Dimensions
Challenges Properties
Definition
Classification
Features
Classification of Materials (Type & Structure)
Composites
Ceramics
Polymeric
Crystalline
Polycrystalline
Amorphous
Metallic
Electronic
Biomaterials
NanomaterialsNanomaterials 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)
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
Internal Internal StructureStructure
Bulk
(Macro & micro)Nano
SizeSize
ShapeShape
Surface area to Surface area to Volume ratioVolume ratio
+
+
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
SCOPE : DOMAIN
Keywords Domain
Particle size Distribution in the continuous phase
Modification of surfaces Interfacial tension
Surfaces Interfaces
Rising volume fraction Homogeneity of phasesof dispersing phase
Domain of Nanotechnology: Multi-phase systems Liquid : Liquid
Solid : Liquid Surfaces and interfaces involving different phases
Gas : Liquid
Gas : Solid
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
SCOPE : DIMENSIONS
What Happens Dimensions
Particle size More from less
Surface area Enhanced coverage
Activity Novel products
Efficiency Improved performanceper unit mass
Maximum possible benefits from minimum possible inputs
Effecting changes through and at atomic scale
Nanomaterials: Features
Synergistic combinations of materials of different kinds & characteristics is possible through nanotechnology
Coatings, Films
Surface modificationSize Reduction
10 nm
1 m
1 cm
Compatibility Huge interfaces
Solid Liquid
Homogeneous solution
Inorganic nanoparticles in a liquid media
+
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
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 evaporationVapour depositionSputtering
Chemical Microemulsion Sol-gel Chemical reduction
Ex-situ
In-situ
•Bulk production
•Reproducibility
•Stability
•Cost
• Single step• Non-agglomeration• Better Stability• Interfacial interaction
Hydration HydrolysisSolubilization Chemical conversionPrecipitation
Concerns
Benefits
Synthesis of Nanomaterials: Ex-situ
TiO2 TiO2
-
-
-
-
-
-
TiO2
TiO2
-
-
-
-
-
-
MonomerPolymer
Surfactant
-
-Radical
Polymerization
10 nm
100 µm
Grinding
Latex Fe2O3-Particles
Fe2O3-ParticlesLatex 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
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
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.
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-1K-1;
Copper (bulk) = 400 Wm-1K-1
Structure of Nanomaterials: Size and Shape
3 - DBulk
x , y , z
Nanocomposite thick film
Rods
TubesWires
d=100 nm
d 100 nm
Example
Nanoparticles
NanofilmsNanocoatings
Application
Bottle-neck
Waveguides
Components for PC, Mobile phones
x , y
x
Nil
Direction of confinement
Unique Properties of Nanomaterials
Nano-sizeBulk Properties
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
Thermal Properties
Transportation of Heat: Nanomaterials
Mechanism of heat travel : Electrons (metals) &
Phonons (non-metals)
Phonons L nanostructure; 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
Pt bulk
Pt 28 nm
Pt 15 nm 0 (
W/m
K)
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
Magnetic Properties
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
Hc
D sp D crit
Single Domain Multi- Domain
Magnetic Properties
Coercive field of Ferromagnetic materials with particle sizeParticle size < Dcrit Single domain Magnetization
Particle size <<< Dcrit Super-paramagnetism
Optical Properties
Optical effects:Metamaterials
=µrr
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
=µrr
µr: Permeability to magnetic fieldr: Permeability to electric field
• µr, r= -ve
• Induced phenomena
µr, r= +veNatural phenomena
Photocatalytic Properties
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 1000nm; thus, energies corresponding to < 1000nm can bring about chemical changes.
The region from 200nm to 1000nm is most useful for photochemical conversion.
Lu
x
400 nm 109 nm 1014 nmWavelength,Short Wavelength
200 nm
SOLAR SELECTIVITY : MATERIALS RESPONSE
Frequency (Hz)
Visib
le
Infrared
Ultraviolet
X-rays
Cosm
ic rays
1081010101210141016101810201022
Rad
iofrequ
ency
Gam
ma rays
Microw
ave
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
PHOTOCHEMICAL CONVERSION : MECHANISM
The Energy E of single photon is given by the Planck equation:- E=h= hc/ Sun light
.
…….. ...………………………………electron
Excitation photon
excited state
Non-radiative relaxation
Conduction band
Valence band
h+
e-
Band gap
E=h
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
=Number of events
Number of photons absorbed
………………………………
Applications of Nanomaterials
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
Nanomaterials: Photochemical Conversion
Advantages
Utilization of unabsorbed part of solar spectrum
Reduced heat dissipation
Quantum Dots
100 nm50 nm
Re
act
ivit
y
10 nmSize (nm)
Nanotubes & nanowires
Mesoporous
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
ZnOCdS
WO3
Band gap Energy
EMS()
TiO2 = 3.20 eV
ZnO = 3.35 eV
WO3 = 2.80 eV
CdS = 2.42 eV
Semiconductors are the most ideal and preferred materials.
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.
CoatingDirt run-off
LightCoating
Roll-off effect
Nano materials
101
Ti alloysBrassMild steelAl alloysCopper
Lead
PE, PAPP, ABSPS, PETPVC
AluminaZirconia
Glass
ConcreteBricks
Metals Polymers Ceramics
Ideal StrengthHigh Strength Building Materials
Yie
ld S
tren
gth
(y)
/ Y
oung
’s M
odul
us (
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
Density (Mg/m3)
Foams
Natural materials
Polymer nano- composites
Polymers
Metals
Metallic nanocomposites
Nanocrystalline metals
Ceramics
Standard composites
Nanotubes & fibers
You
ng’
s M
odu
lus
(GP
a)
Elastomers
Ceramic nanocomposites
0. 1 1.0 10
10-4
1
10
100
10-3
1000
High Strength Materials: Smart Materials
Foams
Natural materials
Polymer CNT composites
Polymers & Elastomers
Metals
Metallic nanocom-posites
Nanocrys-talline metals
Ceramics
Standard composites
Nanowires (Cu, Ag, Au)
Ten
sile
Str
engt
h (
MP
a)
Density (Mg/m3)0. 1 1.0 10 100
0.1
10
100
104
1
105
Polymer-Ceramic nanocomposites
3-D ceramic nanoco-mposite
1-D metallic nanostructures
1-D C-nanostructures
103
Engineering Nanomaterials
Nanomaterials
Green Materials : Nanoengineered Concrete
Nanosilica
Precipitated Silica
Silica fume
MetakaolinFinely ground
mineral additivesPortland cement
Fly ash
Aggregate fines
Natural sand
Coarse aggregates
Nano engineered concreteHigh strength/ high
performance concrete
Conventional concrete
100 101 102 103 104 105 106 108107
10-1
10-2
100
101
102
103
104
105
106
Particle size(nm)
Sp
ecif
ic S
urf
ace
Are
a(K
g/m
2)
Nanoparticles allow better void filling & positive filler effects & improved bond between pastes aggregates; nanosized additives increase strength beyond what is attained with conventional materials
SRI’S EXPERIENCE
SRI has developed nanomaterials for :
Optical applications
Effluent treatment
39393939393939
High Refractive Index Materials
The refractive index of low refractive index materials increases from 1.49 to 1.66.
1 . 4 1
1 . 4 7
1 . 5 3
1 . 5 9
1 . 6 5
1 . 7 1
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0
% o f a d d i t i v e
Ref
ract
ive
ind
ex
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 30Metal salt (% by wt)
Ref
ract
ive
Ind
ex
Barium Hydroxide Lead Monoxide Lanthanum Oxide
High Refractive Index Acrylates
414141414141
High Refractive Index Titanium Nanocomposites
In-situ formation of nanoparticles of TiThe 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
Re
fra
cti
ve
Ind
ex
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
Inte
nsi
ty(a
.u.)
Position (2 Theta)20 30 40 50 60 70 80
External
In-Situ method
TiO2 market procured
TiO2 (Reference)
0 . 0 0
0 . 5 0
1 . 0 0
1 . 5 0
2 . 0 0
2 . 5 0
3 . 0 0
3 . 5 0
4 . 0 0
2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0
W a v e l e n g t h
Ab
so
rba
nc
e
M G A
B C
Semiconductors are used to prepare nanocomposites with enhanced photocatalytic activity
Dye
Nanocomposites & dye degradation
Nanocomposites lead to complete degradation of dyeUseful 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
Deg
rad
ati
on
rate
(%)
Nano
Normal
Nanocomposites for dye degradation
Dye solution
Nanocomposite
Dye removal
Swelled nanocomposite after uptake of dye
Dye removal from effluent
Nanocomposites for Effluent Treatment
THANK YOU
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