Dr. r. k. khandal sikkim

DR. R.K. KHANDALDIRECTOR

TECHNOLOGICAL CHALLENGES FOR MATERIALS OF 21st CENTURY

SHRIRAM INSTITUTE FOR INDUSTRIAL RESEARCH19, UNIVERSITY ROAD, DELHI - 110007

Email : [email protected] Website : www.shriraminstitute.org

OUTLINE Classification of materials Properties of materials

Bulk Materials Internal Structure

NanomaterialsStructure: Size, Shape & Surface area

Designing nanomaterialsApproachesMechanical ParametersIdeal strengthQuantum effectsPhotocatalytic materials

Magnetic materialsOptical materialsAdhesive materials Approaches so farChallenges

Path forward

Defects

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)

101Properties 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 Surface areaarea

+

+

Structure of Bulk Materials : Internal Structure

Atomic Structure

Ionic Bonding e.g. NaCl

Covalent Bonding e.g. CH4, C2H6

Metallic Bonding

Strong High melting, brittleness & poor

electrical conductivity

Aggregate of positively charged cores surrounded by a sea of electrons

Path of electron is completely random Good conductors, highly ductile

Weak Poor ductility & electrical conductivity Brittle & insulators

Shared electrons

FCC

Rock salt

Cesium Chloride

Zinc blende

BCC

HCP

E.g. Cu, Ag, Au, Ni, Al,Fe

E.g. Fe, W, Cr

E.g. Zn, Co, Ti, Fe

E.g. MgO, MnS, LiF, FeO

E.g. ZnTe, SiC

Sim

ple

C

om

ple

x

Some elements exists in more than one crystalline state eg: Iron

Fe BCC750 0C

FCC

RT

125 kbar

HCP

E.g. CsBr, CsI

Crystal Structure


Molecular structure

Repetition of monomer Homo-polymers & Co-polymers Linear, Branched, Cross-linked & Network structures Spaghetti like structure Presence of many Vander-Waals bonds Examples : PE, PS, Nylon, etc.

Random Co-polymer

Alternating Co-polymer

Block Co-polymer

Graft Co-polymer

Linear polymer

Branched polymer

Crosslinked polymer

Polymers


Bulk Materials : Defects

Reasons : Atomic packing problems during processing Formation of interfaces with poor atomic registry Generation of defects during deformation.

106

104

102

100

10-2

10-4

10-6

10-8

Bulk defects

Interfacial defects

Line defects

Atomic point defects

Electronic point defects

Micrometers

Point

Micro defects

Macro defects

Planar

Linear

Volume

Types Classification

VacancySelf interstitialSchottky defectsFrenkel defects

Ductility of metals

Brittleness of ceramics

Formation of cavities/bubbles during casting

Effects :(a)Constructive : C in Fe High strength

0.01% of As in Si in Conductivity of Si by 10,000 times (b)Destructive: Dislocations Deformation in plastics

0 - D

1 - D Rods

TubesWires

2 - D

Basic Geometry Large Scale Forms

Nanocomposite thick film

Nanocomposite thick film

Thin film on substrate Bulk

Nanocomposites

Scope: Ability to design materials with tunable optical, electrical, magnetic, thermal & mechanical properties

(Dimension at micro or macro scale)

d 100 nm

d 100 nm

Structure of Nanomaterials: Size and Shape

Structure Nanomaterials : Shape and Surface area

Different shapes

Sphere

Cylinder Cube

Critical Dimension (nm)Su

rfa

ce t

o V

ol.

rati

o (

nm

-1)

0

0.5

1.0

1.52.0

3.0

3.5

20 40 60 80 100

2.5

Sphere : S : V = 3 : r

e.g.: Shape

Volume remains constant

(10 m) (10nm)

523 nm3

V (10 m)

V (10nm)

5.23 x 1011

523= = 1x109 particles

One single particle of 10 microns can generate 1 billion nanosized particles of 10nm; increase in surface area by a factor of 1000

Surface area

SizeVolume 5.23 x 1011nm3

Number of particles

3.14x108 nm2 314 nm2

Scope : Imparts extraordinary properties to various day-to-day products like self cleaning windows, anti-wrinkle textiles, etc.

AV

=

4r2

4r3/3

2rh r2h

6l 2

l 3

AV

=

AV

= Cylinder : S : V = 2 : r

Cube : S : V = 6 : l

Sphere

Distinct surface to volume ratios

Designing Nanomaterials

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.

Designing Nanomaterials : Mechanical Parameters

PPPE

PETPSPS

PMMAPC

PTFEFoams

Natural materials

Polymers

Non-technical ceramics (Concrete)

MetalsCompositesGFRPCFRP

Technical ceramics

Yo

un

g’s

Mo

du

lus

(GP

a)

Density (Mg/m3)

Flexible polymer foams

Rigid polymer foams

Wood grain

PSiPUPEVAButyl rubber

Elastomers

Ti alloys Ni alloys

Chart for Modulus & Density : Engineering Bulk Materials

10-4

1

10

100

10-3

1000

0. 1 1.0 10

Bulk MaterialsAl2O3,

Si3N4

SiC

W alloys

WCNi alloys

Cu alloysZn alloysPb alloys

Strongest engineering materials reach levels of about 2000 MPa

Foams

Natural materials

Polymer nanocomposites

Polymers

Metals

Metallic nanocomposites

Nanocrys-talline metals

Ceramics

Standard composites

Nanotubes & fibers

Yo

un

g’s

Mo

du

lus

(GP

a)

Density (Mg/m3)

Elastomers

Ceramic nanocomposites

0. 1 1.0 10

10-4

1

10

100

10-3

1000

Chart for Modulus & Density : Engineering Nanomaterials

Nanomaterials

PPPE

PETPSPS

PMMAPC

PTFEFoams

Natural materials

Polymers & Elastomers

MetalsCompositesGFRPCFRPMg Alloys

Ceramics

Yie

ld S

tren

gth

(M

Pa)

Density (Mg/m3)


Rigid polymer foams

Wood

Al alloys

Cork

Si elastomer

Al2O3, SiC, Al alloys,

Ceramics

0. 1

1.0

10

100

1000

10,000

0. 1 1.0 10

Chart for Yield Strength & Density : Engineering Bulk Materials

Al2O3 alloysSiC alloys WC alloysZn alloys

W alloysPb alloysZn alloys

Bulk Materials

Foams

Natural materials

Polymer CNT composites


Metals

Metallic nanocom-posites


Ceramics

Standard composites

Ceramic nanocom-posites

Nanowires (Cu, Ag, Au)

Yie

ld S

tren

gth

(M

Pa)

Density (Mg/m3)0. 1 1.0 10 100

0.1

10

100

104

1

105

103

Nanomaterials

Chart for Yield Strength & Density : Engineering Nanomaterials

PPPE

PETPSPS

PMMAPC

PTFEFoams

Natural materials


Metals

CompositesCFRP, Mg Alloys, Concrete

Ceramics

Ten

sile

Str

eng

th (

MP

a)

Density (Mg/m3)


Rigid foams

Wood

W, Pb, Mg, Ti, Ni, Cu, Zn, Pb alloysSteel,

Cork Si elastomer

0. 1

1.0

10

100

1000

10,000

WC alloys, Al2O3 alloys, SiC alloys, Al alloys

0. 1 1.0 10 100

Chart for Tensile Strength & Density : Engineering Bulk Materials

Bulk Materials

Foams

Natural materials

Polymer CNT composites


Metals

Metallic nanocom-posites


Ceramics

Standard composites

Nanowires (Cu, Ag, Au)

Ten

sile

Str

eng

th

(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

Chart for Tensile Strength & Density : Engineering Nanomaterials

Nanomaterials

Nano materials

101

Ti alloysBrassMild steelAl alloysCopper

Lead

PE, PAPP, ABSPS, PETPVC

AluminaZirconia

Glass

ConcreteBricks

Metals Polymers Ceramics

Ideal Strength

Ideal Strength

To make materials stronger than this is a huge Challenge!

Yie

ld S

tren

gth

( y

) / Y

ou

ng

’s M

od

ulu

s (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

Designing Nanomaterials : Quantum Effects


Conduction bandVacant state



Valence bandOccupied state Valence band

Occupied stateValence bandOccupied state

En

erg

y

Conductor(Metals)

Insulator(Ceramics)

Semi-conductor(Silicon)

No band gap Large band gap Small band gap

Bulk level: Atomic energy levels spread out into energy bands; transfer of electrons from one level to the other is not restricted.

Nano level: Free movement of electrons is restricted due to confinement of electrons.

At the nano level: Quantum effects due to confinement of e- become significant

En

erg

y

En

erg

y


En = Electrons are fully confined

According to quantum mechanics, electron exists inside a deep potential well from which it cannot escape and is confined by the dimensions of the nanostructures

Smaller dimension leads to wider separation of energy levels By spatial confinement of electrons, band gap of a material can be

shifted towards higher frequency

2 h2

2mL2 nx

2 + ny2 + nz

2

0 - D

En = 2 h2

2mL2 nx

2 + ny2 1 - D

En = 2 h2

2mL2 nx

2 2 - D

Electrons confinement in two dimensions

Electrons delocalization in one dimensions

Electrons confinement in one dimensions

Electrons delocalization in two dimensions

h h/2 ; h = Planck’s constant; m = Mass of e- ; L = Width (Confinement)

Implications

Quantum well

Quantum wire

Quantum dot

Designing Nanomaterials : Photocatalytic Materials

Materials with novel approach: Catalytic activity for industrial effluent treatment.

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. Challenge : Maneuvering band gap: Make it sensitive to visible light.

Designing Nanomaterials : Photocatalytic Materials

Designing Nanomaterials : Magnetic Materials

Isolated nanoparticles

Nano particles

Ultrafine Nanoparticles core shell morphology in the matrix

Small magnetic nanoparticles embedded in a chemically dissimilar matrixSmall particles

dispersed in nanocrystalline matrix

Magnetic nanoparticles with polymer coating

Metal-matrix nanocomposites are useful for magnetic applications such as magnetic recordings

Consists of hard magnetic nanoparticles (Nd2Fe14BFm2Fe17N3) dispersed in a soft nanocrystalline phase (Ferrite, Fe3Pt)

< 1 nm: Non-magnetic~ 1-10 nm:Super-paramagnetic

>10 nm: Ferromagnetic

E.g. Mn,Co,Fe & Ni

3M2O3.5Fe2O3

Ni0.5Zn0.4Cu0.1Fe2O3


In the absence of a magnetic field, magnetic interaction results in spin alignment

When a magnetic field is applied in the opposite direction, only the soft phase is able to reverse the magnetization.

When the magnetic field is reversed, magnetism is again reversed in the soft phase

When the applied magnetic field is high enough to reverse the spins in the hard phase; soft phase does not reverse the magnetization

High remenance & high magnetic energy (200 kJ/m3)Ability to maximize the soft phase content to enhance

saturation magnetization

Approach: Mechanical alloying of two phases


This effect is dependent on the size of particles, volume fraction & distribution of each phase

Hard & Soft phases interact magnetically & for best effects, the two phases must be at the nanoscale

Designing Nanomaterials : Optical Materials

=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


Nano pillars Inhomogeneity

Challenge:Selection of materialCreation of different surface

Reflection Transmission Refraction

Non-uniform surface

Camouflaging


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

Camouflaging


Designing Nanomaterials : Adhesive Materials

The ability of a Gecko to scamper up walls has been a very big inspiration for designing a number of adhesives; Useful for the lithography industry where nanosurfaces have been patterned after a gecko’s foot soles.

Clinging ability of Gecko

Intermolecular forces between the paw & the surface Nano-pillars

~ to Gecko paw hair

Designing Nanomaterials : Adhesive Materials

Inert gas condensation Evaporation

colloidal methods

Physical or chemical vapour deposition (PVD

OR CVD)

Extrusion, cryomilling &

sintering

Directional growth from catalyst dots

Templating

Lithographic method

Incorporation of Nanotubes and rods into polymer or metal

matrices

Beating (gold foil) Electrodeposition

PVD,CVD Self-assembled

films

Electrodeposition Physical vapor

deposition Chemical vapor deposition

(1) PVD

(2) CVD

(3) Electrodeposition

1-D

2 D

ime

ns

ion

in

na

no

sc

ale

2-D

1

D

imen

sio

n

in

n

an

os

cal

e

0-D

All

3

Dim

ens

ion

in

na

no

sc

ale

Dim

ensi

on

alit

y

Class 1

Discrete objectsClass 2

Surface featuredClass 3

Bulk structures

Designing Nanomaterials : Approaches So Far

Stability ; AgglomerationStability ; Agglomeration Yield ; Scale-upYield ; Scale-up

SynthesisSynthesis

AssemblyAssembly

ApplicationApplication

Designing Nanomaterials: Challenges

Isolated ; Discrete Isolated ; Discrete Hybrid ; DispersionHybrid ; Dispersion

Mechanical Mechanical Optical Optical Electrical Electrical

MagneticMagnetic ThermalThermal

Utilization of single nanostructure for processing electrical, optical or thermal signals.

Assembling nanostructures for electronic, chemical & other applications.

Path Forward

Development of nanotechnology & nanomaterials for: Development of nanotechnology & nanomaterials for: Storing energy rich gasesStoring energy rich gases

Fuel cellsFuel cells

Solar cellsSolar cells

Photovoltaic textilesPhotovoltaic textiles

Self cleaning, Anti-microbial & other surface properties: Self cleaning, Anti-microbial & other surface properties: Nano paintsNano paints

Nano sealantsNano sealants

Smart materialsSmart materials

Only nanomaterials have made possible the development of Only nanomaterials have made possible the development of futuristic materials with extraordinary propertiesfuturistic materials with extraordinary properties

THANK YOU

Education

Dr. r. k. khandal sikkim