ueet101-nanotech in mechanical engineering

8/7/2019 UEET101-Nanotech in Mechanical Engineering

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Nanotechnology

inMechanical Engineering

Presented By

Pradip MajumdarProfessor

Department of Mechanical EngineeringNorthern Illinois University

DeKalb, IL 60115

UEET 101 Introduction to Engineering


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Outline of the Presentation

Lecture

In-class group activities

Video Clips Homework


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Course Outline

Lecture - I

Introduction to Nano-Technology in Engineering

Basic concepts

Length and time scales

Nano-structured materials

- Nanocomposites- Nanotubes and nanowire

Applications and Examples

LectureII

Nano-Mechanics

Nanoscale Thermaland FlowPhenomena

Experimental

Techniques

Modeling and

Simulation


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Lecture Topics

We will address some of the key issues of nano-technology in Mechanical Engineering.

Some of the topics that will be addressed arenano-structured materials; nanoparticles andnanofluids, nanodevices and sensors, andapplications.


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Major Topics in Mechanical Engineering

Mechanics:Statics : Deals with forces, Moments,equilibrium of a stationary body

Dynamics:Deals with body in

motion -velocity, acceleration,torque, momentum, angularmomentum.

Structure and properties ofmaterial (Including strengths)

Thermodynamics, power

generation, alternate energy

(power plants, solar, wind,

geothermal, engines)

Design of machines andstructures

Dynamics system, sensorsand controls

RoboticsComputer-Aided Design

(CAD/CAM)

Computational FluidDynamics (CFD) and

Finite Element Method

Fabrication and

Manufacturing processes


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x = 10 mm x = 250 mm x = 500 mm x = 750mm x = 1000mm

DC power Supply

(-)(+)

CathodeElectrode

AnodeElectrode

Electron flow

Electrolyte membrane

H

e2

2H

Bipolar Plates

MEAs

Diesel Engine Simulation Model

Fuel Cell Design

and Development

No slip

conditionSlip Conditions

Flow in micro channel


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Length Scales in Sciences and

Mechanics

1010

810

610

QuantumMechanics

MolecularMechanics

Nano-mechanics

310

Micro-mechanics

010

Macro-Mechanics

Regimes of Mechanics

Length Scales (m)

Quantum Mechanics:Deals with atoms -Molecular Mechanics:Molecular Networks -Nanomechanics:Nano-Materials -Micromechanics:

Macro-mechanic:

Continuumsubstance


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Quantum and Molecular MechanicsAll substances are composed molecules or atoms in

random motion. For a system consisting ofcubeof 25-mm on each side

and containinggaswith atoms. To specify the position of each molecule, we need to

three co-ordinates and three component velocities So, in order to describe the behavior of this system

form atomic view point, we need to deal with at leastequations.

This is quite a computational task even with the mostpowerful (massively parallel multiple processors)computer available today.

There are two approaches to handle this situations:

Microscopicor Macroscopicmodel

20106

2010


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Microscopic Vs Macroscopic

Approach -1:Microscopic viewpointbased onkinetic theory and statistical mechanics On the basis of statistical considerations and probability theory,

we deal with average values of all atoms or molecules and inconnection with a model of the atom.

ApproachII Macroscopic view point

Consider gross or average behavior of a number of moleculesthat can be handled based on the continuum assumption.

We mainly deal with time averaged influence of many molecules. These macroscopic or average effects can be perceived by our

senses and measured by instruments. This leads to our treatment of substance as an infinitely divisible

substance or continuum.


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Breakdown of Continuum Model

To show the limit of continuum or macroscopic model, let usconsider the concept of density:

Density is defined as the massper unit volume and expressed as

Where is the smallest volume for which substance can beassumed as continuum.

Volume smaller than this will lead to the fact that mass is notuniformly distributed, but rather concentrated in particles asmolecules, atoms, electrons etc.

Figure shows such variation in density as volume decreases belowthe continuum limit.

V

mlim

/VV

/V

V


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Macroscopic Properties and

MeasurementPressure

Pressure is defined as the

average normal-component

of force per unit area and

expressed as

Where is the smallestvolume for which substance canbe assumed as continuum.

A

FP n

/AA

lim

/A

A

F

nF

Pressure

Gauge

Gas

Tank

Pressure

Measurement

For a pressure gauge, it is theaverage force (rate of change ofmomentum) exerted by therandomly moving atoms ormolecules over the sensors area.Unit: Pascal (Pa) or

2

m

N


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Introduction- Nanotechnology

Nanoscale uses nanometer as the basic unit ofmeasurement and it represents a billionth of ameteror one billionth of a part.

Nanotechnology deals with nanosized particlesand devices

One- nmis about 3 to 5 atoms wide. This is verytiny when compared normal sizes encounter day-

to-day.- For example this is 1/1000th the width of human

hair.


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Any physical substance or device with structural

dimensions below 100 nm is called nanomaterialor nano-device.

Nanotechnology rests on the technology that

involves fabrication of material, devices andsystems through direct control of matteratnanometer length scaleor less than 100 nm.


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Nanoparticles can be defined as building blocks ofnanomaterials and nanotechnology.

Nanoparticles include nanotubes, nanofibers, fullerenes,dendrimers, nanowires and may be made of ceramics,metal, nonmetal, metal oxide, organic or inorganic.

At this small scalelevel, the physical, chemical andbiological properties of materials differ significantly fromthe fundamental properties at bulk level.

Manyforces or effectssuch inter-molecular forces,

surface tension, electromagnetic, electrostatic, capillarybecomes significantly more dominant than gravity.

Nanomaterial can bephysically and chemicallymanipulatedto alter the properties, and these properties

can be measured using nanoscale sensors and gages.


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A structure of the size of an atom represents one of thefundamental limit.

Fabricating or making anything smaller requiremanipulation in atomic or molecular level and that islike changing one chemical form to other.

Scientist and engineers have just started developing new

techniques for making nanostructures.

Nanoscience

Nanofabrication Nanotechnology

The nanoscience is matured.

The age of nanofabrication is

here.

The age of nanotechnology -that is the practical use ofnanostructure has just started.


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Nanotechnology in Mechanical

EngineeringNew BasicConcepts

Nano-Mechanics

Nano-ScaleHeat Transfer

Nano-fluidics

Applications


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Applications

Structural materials

Nano devices and sensors

Coolants and heat spreaders

Lubrication Engine emission reduction

Fuel cellnanoporouselectrode/membranes/nanocatalyst

Hydrogen storage medium

Sustainable energy generation - Photovoltaic cells forpower conversion

Biological systems and biomedicine


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Basic Concepts

Energy Carriers

Phonon:Quantized lattice vibration energy with wavenature of propagation

- dominant in crystalline material

Free Electrons:

- dominant in metals

Photon:Quantized electromagnetic energy with wavenature of propagation

- energy carrier of radiative energy


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Length Scales

Two regimes:

I. Classical microscale size-effect domain Useful formicroscale heat transfer in micron-size environment.

cL

m

Where

characteristic device dimension

mean free path length of the substance

)1(O

m

cL

II. Quantum nanoscale size-effect domainMore relevant to nanoscale heat transfer

Wherecharacteristic wave length of the electronsor phonons

)1(Oc

cL

c


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This length scale will provide the guidelines foranalysis method- both theoretical andexperimental methods:

classical microscale domainor nanoscalesize-effect domain.


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Flow in Nano-channels

The NavierStokes (N-S) equation of continuum model fails when the

gradients of macroscopic variables become so steep that the length scale is of

the order of average distance traveled by the molecules between collision.

Knudsen number ( ) is typical parameter used to classify the length scale

and flow regimes:L

Kn

Kn < 0.01: Continuum approach with traditional Navier-Stokes

and no-slip boundary conditions are valid.

0.01


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Time Scales

Relaxation timefor different collision process:

Relaxation time forphonon-electron

interaction:

Relaxation time for electron-electron

interaction:

Relaxation time forphonon-phonon

interaction:

)s11

10(O

)s13

10(O

)s13

10(O


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Nanotechnology: Modeling

Methods

Quantum Mechanics

Atomistic simulation

Molecular Mechanics/DynamicsNanomechanics

Nanoheat transfer and Nanofluidics


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Models for Inter-molecules Force

- Inter-molecular Potential

Model

- Inverse Power Law Model or

Point Centre of Repulsion

Model

- Hard Sphere Model

- Maxwell Model

- Lennard-Jones Potential

Model

Inter-Molecular Distance

Force

Inter-molecularPotential Model


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Nanotools

Nanotools are required for manipulation of matter at

nanoscale or atomic level. Certain devices which manipulate matter at atomic or

molecular level are Scanning-probe microscopes,atomic force microscopes, atomic layer depositiondevicesand nanolithography tools.

Nanolithography means creation of nanoscale structureby etching or printing.

Nanotools comprises of fabrication techniques, analysisand metrology instruments, software fornanotechnology research and development.

Softwares are utilized in nanolithography, 3-D printing,nanofluidics and chemical vapor deposition.


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Nanoparticles and Nanomaterials

Nanoparticles:

Nanoparticles are significantly larger than individualatoms and molecules.

Nanoparticles are not completely governed by eitherquantum chemistry or by laws of classical physics.

Nanoparticles have high surface area per unit volume.

When material size is reduced the number of atoms on

the surface increases than number of atoms in thematerial itself. This surface structure dominates theproperties related to it.

Nanoparticles are made from chemically stable metals,

metal oxides and carbon in different forms.


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Carbon -Nanotubes Carbon nanotubes are hollow

cylinders made up of carbon atoms. The diameterof carbon nanotube is

few nanometersand they can beseveral millimeters in length.

Carbon nanotubes looks like rolled

tubes of graphite and their walls arelike hexagonal carbon rings and areformed in large bundles.

Have high surface area per unitvolume

Carbon nanotubes are 100 timesstronger than steel at one-sixth of theweight.

Carbon nanotubes have the ability tosustain high temperature ~ 2000 C.

b


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There are four types of carbonnanotube: Single Walled CarbonNanotube (SWNT),Multi WalledXarbon nanotube (MWNT), Fullereneand Torus.

SWNTs are made up of singlecylindrical grapheme layer

MWNTs is made up of multipleGrapheme layers.

SWNT possess important electricproperties which MWNT does not.

SWNT are excellent conductors, so findsits application in miniaturizing

electronics components.


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Formed by combining two or morenanomaterials to achieve better

properties.

Gives the best properties of eachindividual nanomaterial.

Show increase in strength, modulus ofelasticity and strain in failure.

Interfacial characteristics, shape,structure and properties of individualnanomaterials decide the properties.

Find use in high performance,lightweight, energy savings andenvironmental protection applications

- buildings and structures, automobiles

Nanocomposites


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Examples of nanocomposites include nanowiresand metal matrix composites.

Classified into multilayered structures and inorganic ororganic composites.

Multilayered structures are formed from self-assembly ofmonolayers.

Nanocomposites may provide heterostructures formed from

various inorganic or organic layers, leading to multifunctionalmaterials.

Nanowires are made up of various materials and find its

application in microelectronics for semiconductor devices.

Nanostructured Materials


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All the properties of nanostructured

are controlled by changes in atomicstructure, in length scales, in sizesand in alloying components.

Nanostructured materials areformed by controlling grain sizes andcreating increased surface area per

unit volume.

Decrease in grain size causesincrease in volumetric fraction of

grain boundaries, which leads tochanges in fundamental properties of

materials.

Nanostructured Materials

Different behavior of atoms

at surface has been observed

than atom at interior.

Structural andcompositional differences

between bulk material and

nanomaterial cause change

in properties.


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The size affected properties are color, thermal conductivity,mechanical, electrical, magnetic etc.

Nanophase metals show increase in hardness and modulusof elasticity than bulk metals.

Nanostructured materials are produced in the form of

powders, thin films and in coatings.

Synthesis of nanostructured materials take place by Top Down or Bottom- Up method.- In Top-Down method the bulk solid is decomposed into

nanostructure.- In Bottom-Up method atoms or molecules are

assembled into bulk solid. The future of nanostructured materials deal with controlling

characteristics, processing into and from bulk material and


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Nanofluids

Nanofluidsare engineered colloid formed with stablesuspemsions of solid nano-particles in traditional baseliquids.

Base fluids: Water, organic fluids, Glycol, oil, lubricantsand other fluids

Nanoparticle materials:

- Metal Oxides:- Stable metals: Au, cu- Carbon: carbon nanotubes (SWNTs, MWNTs),

diamond, graphite, fullerene, Amorphous Carbon

- Polymers : Teflon

3O2Al 2ZrO 2SiO 4O3Fe


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Nanofluid Heat Transfer

Enhancement

Thermal conductivity enhancement

- Reported breakthrough in substantially increase

( 20-30%) in thermal conductivity of fluid byadding very small amounts (3-4%) of suspendedmetallic or metallic oxides or nanotubes.

Increased convective heat transfercharacteristic for heat transfer fluids as

coolant or heating fluid.

-


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Nanofluids and Nanofludics

Nanofluids have been investigated

- to identify the specific transport mechanism

- to identify critical parameters

- to characterize flow characteristics in macro,

micro and nano-channels

- to quantify heat exchange performance,

- to develop specific production, management

and safety issues, and measurement and

simulation techniques


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Nano-fluid Applications

Energy conversion and energy storage system

Electronics cooling techniques

Thermal management of fuel cell energy systems

Nuclear reactor coolants

Combustion engine coolants

Super conducting magnets Biological systems and biomedicine

Nano Biotechnolog


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Nano-Biotechnology

When the tools and processes of nanotechnology are

applied towards biosystems, it is called nanobiotechnology. Due to characteristic length scale and unique properties,

nanomaterials can find its application in biosystems.

Nanocomposite materials can play great role indevelopment of materials for biocompatible implant.

Nano sensors and nanofluidcs have started playing animportant role in diagnostic tests and drug delivering system

for decease control.

The long term aim of nano-biotechnology is to build tinydevices with biological tools incorporated into it diagonisticand treatment..


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National Nanotechnology Initiative

in Medicine

Improved imaging (See: www.3DImaging.com)

Treatment of Disease

Superior Implant Drug delivery system and treatment using

Denrimers, Nanoshells, Micro- and Nanofluidicsand Plasmonics


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-Nano-particles deliverstreatment to targeted area or

targeted tumors- Release drugs or releaseradiation to heat up and destroytumors or cancer cells

- In order to improve thedurability and bio-compatibility,the implant surfaces are modified

with nano-thin film coating(Carbon nano-particles).

-An artificial knee joint or hipcoated with nanoparticles bonds tothe adjacent bones more tightly.


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Self Powered Nanodevices and

Nanogenerators

Nanosize devices or machined need nano-size powergenerator call nanogeneratorswithout the need of abattery.

Power requirements of nanodevices or nanosystems aregenerally very small

in the range of nanowatts to microwatts.

Example: Power source for a biosensor

- Such devices may allow us to develop implantablebiosensors that can continuously monitor humansblood sugar level


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Waste energy in the form of vibrations or even the human pulsecould power tiny devices.

Arrays of piezoelectric could capture and transmit that waste energy

to nanodevices There are manypower sources in a human body:

- Mechanical energy, Heat energy, Vibration energy,Chemical energy

A small fraction of this energy can be converted into electricity topower nano-bio devices.

Nanogenerators can also be used for other applications- Autonomous strain sensorsfor structures such as bridges- Environmental sensors for detecting toxins

- Energy sensorsfor nano-robotics- Microelectromecanical systems (MEMS) or

nanoelectromechanical system (NEMS)- A pacemakers battery could be charged without

requiring any replacement


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Nano-sensor and Nano-generator

Nano-sensor Capacitor Nano-generator


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Example: Piezoelectric

Nanogenerator

Piezoelectric Effect

Some crystalline materials generates electrical voltagewhen mechanically stressed

A Typical Vibration-based Piezoelectric Transducer- Uses a two-layered beam with one end fixed

and other end mounted with a mass

- Under the action of the gravity the beam is bent with

upper-layer subjected to tension and lower-layer

subjected to tension.


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Conversion of Mechanical Energy to Electricity

in a Nanosystem

Tension Compression

Nanowire

Tension Compression

Nanowire

Rectangular electrode

with ridged underside.Moves side to side in

response to external

motion of the

structure

Array of

nanowires (Zinc

Oxide) withpiezoelectric and

semiconductor

properties

Gravity do not playany role for motion

in nanoscale.

Nanowire is flexed

by moving a ridgedfrom side to side.


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Example: Thermo Electric Nano-generator

Thermoelectric generator relies on the Seebeck Effectwhere an electric potentialexists at the junction oftwo dissimilar metals that are at different temperatures.

The potential difference or thevoltage produced isproportional to the temperature difference.

- Already used in Seiko Thermic Wrist Watch


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Bio-Nano Generators

Questions:1. How much and what different kind of energy

does body produce?

2. How this energy source can be utilized toproduce power.

3. What are the technological challenges?

ueet101-nanotech in mechanical engineering

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