overview of nanoparticle

7/29/2019 Overview of Nanoparticle

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Overview of Nanoparticle & itsapplications to Lubricants

Dr.K.Balamurugan

Associate Professor/Mech. Engg.IRTT, Erode

[email protected]


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Agenda Nanotechnology

Nanoparticles

Lubricants

HS&E issues


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"There's plenty of room at the bottom."

Richard P. Feynman, Ph.D.


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What is

Nanotechnology?


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Nanotechnology is an enabling

technology that will change thenature of almost every human-madeobject in the next century.

-National Science and Technology Council


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What is Nanotechnology?Nanotechnology is about:

Making small objects Manipulating small objects

Creating new materials by varying the

size of the objects Building structures from small objects

This slide is adapted from the presentation on AnIntroduction to Nanotechnology, by Terry Bigioni, posted at

http://www.homepages.utoledo.edu/tbigion/BigioniGroup/Outreach_Home.html


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WHAT IS NANOTECHNOLOGY?

* 1 millimeter = 1,000 micrometers;1 micrometer = 1,000 nanometers

Source: "Nanotech: The Tiny Revolution" by CMP Cientfica (November 2001)

Structures(e.g.materials)

Devices(e.g. sensors)

Systems(e.g. NEMS)

Nanotechnology is themanipulation of matterat the nanometer*scale to create novel

structures, devices andsystems.


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Building Complex Structures with SmallObjects

Top-down(i.e. Lithography)

Bottom-up(i.e. Self-assembly)

Mixing large objects with small

ones(i.e. nanocomposites) Carbon matrix

Nanotube bundles

Composite

fabrication


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Starting frombig thingshas meant producing things with the precision that

we were able to achieve, but -at the same time-

producing lots ofwaste or pollution,and consuming a lot of energy.

As we got better at technology,

precision improved and

waste/pollution diminished,but the approach

was still the same.


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Starting fromsmall things

means absolute precision(down to one single atom !),

complete control of processes(no waste?) and

the use ofless energy(withless CO2, less greenhouse

effect, perhaps you

heard about that on TV).


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Advantages of

starting fromsmall thingsthe distance between the centre of two footballs isbigger than the distance between the centre of two

nuts smaller means nearer(and quicker to connect)

you can dissolve sugar or salt quicker

when it is in powder form and slowerwhen it is in the form of crystals orblocks smaller can becomemore reactive


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Nanotechnology The science of constructing unique materials at

the molecular level, in the scale of 1-100nanometers.

1 nanometer is 1/1000 of a micron, or 1 billionthof a meter.

At this level, it is possible to vary fundamentalproperties of materials (for instance, melting

temperature, magnetization, charge capacity)without changing the chemical composition.


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A DIVERSE SET OF OPPORTUNITIES

1-4

5-8

9-14

15+

Composites

Solar

cells

Lighting

Foodpackaging

Energy/

fuel cells

Energy,

Industrial

PortableEnergy

cells

Bio-materials

Tissue/organregen

NanobioNEMS

Smartimplants

Drugdelivery

Medicaldiagnostics

Medical

applications

Nano-arrays

Years

Chemical

catalysts

Textiles

Coatings &

Powders

LubricantsCoatings

Cosmetics

Paints

Micro-processors

Quantumcomputing

Simple

ICs

Memory/Storage

devices

Sensors

Displays

Devices &Microelectronics

Molecular

circuitry


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Nanotechnology Smaller is Different:

Surface-Effects Dominate

Ratio of surface area to volume become very large

The Macro World is Dominated by: Gravity

Inertia

Magnetism

The Micro World is Dominated by:

Electrostatics Surface Tension

van der Waals Forces

Example: water cannot flow through microfluid tubesdue to its large surface tension.


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Nanoparticle

Particle size less than 100 nm

Physical changes

Surface area to the volume Classical mechanics to quantum mechanics

Transparent

ultrafine particles, clusters, nanocrystals,quantum dots

Organic an inorganic materials Carbon, Graphite, Copper, Mx2, silicate, Ceramic


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Top-down Approaches

milling or attrition

thermal cycles

10 ~ 1000 nm; broad size distribution

varied particle shape or geometry

impurities for nanocomposites and nanograined

bulk materials (lower sintering

temperature)


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Bottom-up Approaches

Two approaches

thermodynamic equilibrium approach generation of supersaturation nucleation

subsequent growth

kinetic approach limiting the amount of precursors for the

growth

confining in a limited space


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Nanoparticle - Production Techniques

Vapour condensation

Chemical synthesis

Solid state process


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Vapour condensation

It involves evaporation of solid metal followedby rapid condensation to form nanosized

clusters that settle in the form of powder.

Used to make metallic and metal oxideceramic nanoparticles


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Vapour condensation

Inert gases are used to avoid oxidation whencreating metal nanoparticles

Reactive oxygen atmosphere is used toproduce metal oxide ceramic nanoparticles.

Final particle size is controlled by processparameters such as temperature, gasenvironment and evaporation rate


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Vapour condensation

Vacuum evaporation on running liquids(VERL)

This uses a thin film of a relatively viscousmaterial, an oil, or a polymer, for instance, ona rotating drum

Chemical Vapour Deposition

Thin films, particles

Adv. : Low contamination levels


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Chemical synthesis

Most widely used technique

It consists essentially of growing nanoparticles ina liquid medium composed of various reactants

Sol-Gel method, SonoChemistry, Precipitation

Better in controlling the final shape of theparticles


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Chemical synthesis

Choosing chemicals that form particles thatare stable, and stop growing, at a certain size

Low-cost and high volume

Contamination by the chemicals

Create surface coatings


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Arrested precipitation

Precipitation under starving conditions: a largenumber of nucleation centers are formed by

vigorous mixing of the reactant solutions.

If concentration growth is kept small, nucleigrowth is stopped due to lack of material.

Particles had to be protected from Oswald Ripening by stabilizers


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Oswald Ripening

The growth mechanism where smallparticles dissolve, and are consumed by

larger particles. As a result the averagenanoparticle size increases with timeand the particle concentration

decreases. As particles increase in size,solubility decreases.


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Solid state process

Grinding or milling can be used tocreate nanoparticles

The milling material, milling time andatmospheric medium will affect theresult

Contamination from the milling material


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Stabilization of Nanoclusters AgainstAggregation

1. Electrostatic stabilizationAdsorption of ions to thesurface. Creates an electrical

double layer which results in aCoulombic repulsion forcebetween individual particles

2. Steric StabilizationSurrounding the metal centerby layers of material that aresterically bulky,Examples: polymers,surfactants, etc

d+

d+

d+

d+

d+

d+

d+

d+

d+

d+

---

---

--

-

-

--

-

-

-- -

--

--

--

-

- - -

-- -

----

-+

+

+

+

+

++


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StabilizersRole of stabilizers: Stabilizing agents/ligands/cappingagents/passivating agents

prevent uncontrollable growth of particles prevent particle aggregation control growth rate controls particle size Allows particle solubility in various solvents


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Other Common Stabilizers1. Organic ligands

Thiols (thioethanol, thioglycerol, etc) Amines

phosphates

2. Surfactants

3. Polymers

4. Solvents (ether, thioether)

5. Polyoxoanions


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Table 3.1


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Common Methods for NanoparticleCharacterization

Particle

Size

Surface

Area

Surface state

Surface

composition

Surface

structure;

TopographySurface

ComplexesElectron Microscopy

X-ray diffraction

Magnetic Measurements AES,

XPS,

SIMS,

EPMA,

EXAFS

LEED

SEM

TEM

EXAFS

IR, UV-Vis, ESR, NMR, Raman


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