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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Structure of materials
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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Structure of materials
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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Structure of materials
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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Structure of materials
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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Structure of materials
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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Nanotechnology and materials
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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Nanotechnology and materials
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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Nanotechnology and materials
science and engineering
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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Nanotechnology and materials
science and engineering
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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Nanotechnology and materials
science and engineering
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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Scanning Probe Microscopy of Nano-
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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Scanning Probe Microscopy of Nano-
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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Scanning Probe Microscopy of Nano-
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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Scanning Probe Microscopy of Nano-
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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Scanning Probe Microscopy of Nano-
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