lecture structure of materials nanotechnology

8/2/2019 Lecture Structure of Materials Nanotechnology

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Nanotechnology and the Structure of

Materials

Five different levels of structure of

materials may be examined and

describedAtomic structure

Short-and long-range arrangements

NanostructureMicrostructure, and

Macrostructure


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Structure of materials

Atomic Structure

Atomic or ionic arrangements up

to ~ 0.1 nm (10-10 meters)

Bonding type leads to different

atomic or ionic arrangements in

materials

Diamond from C-C covalent bonds

used as thin films for wear-resistant

edge in cutting tools


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Short-range atomic arrangement

Atomic or ionic arrangements from 0.1 -

1nm (10-10 - 10-9 meters)

Atoms or ions show order in theirarrangement over relatively short

distances; arrangement of atoms or ions

extends only to their nearest neighbors

Ions in silica (SiO2) glass is amorphous

due to short-range arrangement and forms

basis of the fiber-optics industry


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Long-range atomic arrangement

Repetitive three-dimensional patterns or

arrangements of atoms or ions in

crystalline materials They range from ~ 10nm (10-8 meters)

up to cm; include Lead-zirconium-

titanate-ions (PZT) arranged in tetragonal

and/or rhombohedral crystal structures

These crystalline materials are

piezoelectric, that is, they develop a

voltage and a spark on applying pressure


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Nanostructure

Structure of materials from 1 - 100nm

(10-9 - 10-7 meters)

Nano-sized particles of iron oxide (~ 510 nm) typical example

Nano-sized iron oxide particles used in

liquid magnets as cooling (heat transfer)

medium for loadspeakers


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Microstructure

Structure of materials from ~>102

105nm (10-7 - 10-4 meters) or 0.1100m

Fine grain of crystalline structureIn general, finer grain size leads to

higher strength at room temperature


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Macrostructure

Structure of materials ~>105 nm

(~10-4 m or 100m)

Relatively thick coatings such as

paints on automobiles

Used for aesthetics and also to

provide corrosion resistance


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Nanotechnology

What is nanotechnology?Nano is 10-9 and a nano meter 10-9 meters (or 1nm

about the size of ten atomone carbon atom is

~0.15nm)Technology is is the building of useful things from

scientific principles

Nanotechnology means building useful things atthe 10-9 meters level

Nanotechnology may therefore, be defined as thestudy, development and processing of materials,devices and systems at atomic, molecular ormacromolecular scale


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Nanostructure: A nanometer (nm) is 10-9 meter (1 m = 3.28 ft).

Argon 0.3 nm

CH4 0.4 nm

H2O 0.3 nm

Red Blood Cell

2000x7000 nm

Nanotech: from1 nm to ~100 nmAlbumin 6.5 nm

Ribosome 25 nm


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Dimensions at the nanoscale

Argon 0.3 nm

CH4 0.4 nm

H2O 0.3 nm

HIV 125 nmRed Blood Cell

2000x7000 nm~1 nm ~100 nmAlbumin 6.5 nm

Ribosome 25 nm


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Nanotechnology

What is nanotechnology (cont..)?

Nanotechnology involves the controlled

creation and use of structures, devices andsystems with a length scale of 1100 nm

It covers the design, behavior and modeling

nanostructures, nano-metrology andcharacterization


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Nanotechnology

What is nanotechnology (cont..)? Nanoscale materials and devices may be

fabricate/created using two different approaches

Bottom-up approach or methods where nano-materials or structures are fabricated from build-up of atoms or molecules in a controlled manner

Top-down methods where nano-fabrication and

micro-technologies used to fabricate nano-scalestructures and devices from a block of thematerial. The size limit of smallest features createddepending on the technology


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Nanotechnology and materials

science and engineeringSome nanotechnology areas of interest

Nano-structured materials

Self organizing and self assembling

molecular structures

Biological and biomedical systems

Scanning probe microscopy


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Polymorphism Allotropy is ability of a substance to exist in more than one physical form

e.g., Carbon has four allotropes that include diamond and graphite

Polymorphism is allotropy of solids which relies solely on differences in

crystal structure, that is two or more distinct crystal structures for the same

material e.g., -Fe has BCC structure and -Fe FCC

Allotropes of carbon:

diamond, graphite,Buckminsterfullerene

C60 , carbon nanotubesBCC

FCC

BCC

1538C

1394C

912C

-Fe

-Fe-Fe

liquid

iron system


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Allotropy of Carbon and Carbon

Nanotubes

The four allotropes of carbon a) Diamond b) Graphite

c) Buckminsterfullerene (C60), third allotrope of carbon

Consists of 60 carbon atoms of 12 regular pentagons

and 20 regular hexagons that fit together perfectly asa soccer ball

The soccer ball shape has 60 corners where eachcarbon atom at the corner has two single bonds andone double bond

(d) Carbon nanotubes, the fourth allotrope of carbon

Envisioned as sheets of graphite rolled into tubes withhemispherical fullerene (C60) caps on the ends

Typically 125 nm in diameter and a few microns(103 nm) long


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Nanotechnology and materials science and

engineering

Nano-structured materials Nano-sized iron oxide particles, cerium oxide, CeO2 and zinc

oxide, ZnO nanocrystals, and quantum dots (which areflorescent semiconductor nanocrystals)

Buckminsterfullerene (C60

), third allotrope of carbon

Carbon nanotubes, the fourth allotrope of carbon


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Types of Carbon Nanotubes:Types of Carbon Nanotubes:

1.Armchair. 2. Zigzag. 3. Chiral


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Nanostructure: Zeolites

Silicate-Aluminate


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science and engineeringSome useful properties of nano-

structured materials

The small (nano-) size of the materialsresults in:

Higher active surfaces per unit of volume andmass

Increased catalytic activity and water solubilityIncreased hardness, ductility, magnetic coupling

and selective absorption


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Catalysts and Surface Defects

A catalyst increases the rate

of a chemical reaction

without being consumed

Active sites on catalysts are

normally surface defects

.

Single crystals of

(Ce0.5Zr0.5)O2

used in an

automotive

catalytic converter


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science and engineering

Applications of nano structured materials Nano-sized iron oxide particles used in liquid magnets as

cooling (heat transfer) medium for loudspeakers

Quantum dots may be used for high resolution cellularimaging

Gold nanorods ~200 times smaller than red blood cells usedfor ultra-sensitive medical imaging technique for cells

Carbon nanotubes which can accumulate in tumors absorbnear-infrared light that is harmless to human tissue leads tothe absorbed light releasing excess energy as heat to destroythe tumor

Polymer-based nanoparticles used to improve drug delivery


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Gas absorbed in carbon nanotubes


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Inclusion in zeolitesInclusion in zeolites


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Self-organizing and self-assembling molecularstructures A Bottom-up method where nano-materials or structures

are fabricated by molecular self-assembly

Atoms, molecules, and molecular aggregates organize andarrange themselves without human intervention

Inorganic and organic monolayers 15 nm in thickness thatare ~ only one molecule or even one atom thick with a widerange of excellent properties including being chemicallyactive, as well as being dense and hard for wear resistance

Monolayers deposited on semiconducting substrates as basisof solar energy cells, and sensors


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Self-organizing and self-assembling molecularstructures Monolayers of different materials forming multilayers with

specific magnetic properties for magnetic recording , andhigh corrosion resistance

Self organizing and self-assembly molecular systems thatmimic the self assembly of molecules in biology as in theaddition of water to lipids which leads to self-assembly intoordered structures with hydrocarbon tails on the inside andthe head group projecting into the water.

The self-assembly ordered structures may be used for

incorporating protein namomachines e.g. ATPase ananoturbine that is embedded in a lipid membrane thatconverts ADP to ATP the energy currency of the cell. Nano-sized biosensors formed by self-assembly based on biology


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Biological and biomedical systems Both Bottom-up and Top-down methods of

nanotechnology approaches to drug delivery

Bottom-up approach of using nanoparticles frombiodegradable polymers or liposomes (special lipid bilayer)that encapsulate the drug with targeting molecules such asantibodies or proteins on the surface of the nanoparticle thattargets specific cell types for controlled delivery of drug

Top-up micro-fabricated drug delivery chip withreservoirs that contain the drug and as the cap of each

reservoir is removed the drug is released Bottom-up molecular self-assembly of small building

blocks used to generate tissue engineering scaffolds


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Microscopy

Optical resolution ca. 10-7

m = 0.1 m = 100 nmFor higher resolution need higher frequency

X-Rays? Difficult to focus.

Electrons

wavelengths ca. 3 pm (0.003 nm)

(Magnification - 1,000,000X)

Atomic resolution possible

Electron beam focused by magnetic lenses.


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Scanning Probe Microscopy of Nano-

materials

Scanning Probe Microscopy Ultra-precision instruments with accuracies in the

order of 1 nm or even 0.1 nm needed for research

and development and manufacturing in the nano-regime

Transmission electron microscope (TEM) was thefirst tool that allowed us to see and count atoms

Scanning electron microscope (SEM) followed the

TEM and produces a sharp, three dimensionalview of a specimen

TEM however, produces images of greatermagnification


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materials

Scanning Probe Microscopy

Scanning probe microscopy (SPM) is a general

term that includes scanning tunneling microscopy

(STM) and atomic force microscopy (AFM) as

typical examples

Scanning probe microscopy (SPM) used to image

surfaces at the nanometer scale


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materials

Scanning Probe Microscopy Scanning probe microscopy (SPM) uses a fine

probe that is either scanned over a surface or the

surface is scanned under the probe, instead ofusing a bean of elections as in TEM and SEM

The use of a probe eliminates the constraintimposed by the wavelength of a beam of electrons

Resolutions obtained using SPM range from

resolving atoms to giving true 3-D maps of surfacesof samples with 0.11 nm resolution possible


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materials

Scanning Tunneling Microscopy

A scanning tunneling microscope (STM) scans a sharp tip

over the surface of a sample, and a voltage applied to the tip

Electrons from the tip tunnel or leak to the sample or viceversa depending on the bias voltage when the tip is ~1 nm

from the sample

The resulting current is a function of the tip to the sample

distance, and measurements of current used to map the

sample surface The sample surface can be imaged at an extremely small scale

down to resolving individual atoms


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Atoms can be arranged andimaged!

Carbon monoxide

molecules arranged ona platinum (111)

surface.

Photos produced from

the work of C.P. Lutz,

Zeppenfeld, and D.M.

Eigler. Reprinted with

permission from

International BusinessMachines Corporation,

copyright 1995.

Iron atoms arranged on a

copper (111) surface.

These Kanji characters

represent the word

atom.

Scanning Tunneling Microscopy

(STM)


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materials

Atomic Force Microscopy

Atomic force microscope (AFM) developed to overcome the

basic drawback of STM requiring conducting or

semiconducting surfaces for imaging AFM therefore, images surfaces including polymers,

ceramics, composites, glass and biological samples

The AFM scans a sharp tip (nano-sized of about 500 nm long

and 100 nm wide) held at the apex of a cantilever over the

surface of a sample The extension of a crystal called a piezo on the cantilever is

responsible for the movement of the tip across the surface


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materials

Atomic Force Microscopy The force between the tip and the surface of the sample

causes the cantilever to bend

A device called an optical lever measures the deflection of the

cantilever The optical lever consists of a laser beam and a position-

sensitive photodetector

The position-sensitive photodetector can measure changes inposition of the incident laser beam as small as 1 nm, thusgiving sub-nanometer resolution

In contact mode AFM, an actuator moves the sample withrespect to the tip in order to maintain a constant deflectionand the surface of the sample is thus mapped as a function ofheight

lecture structure of materials nanotechnology

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