Carbon Nanotubes: The exciting future of fullerenes

Carbon Nanotubes:The exciting future of

fullerenesPresented By:• David Chaar• Steven Hering• Phillip Thane• Kori Mondin

Papers used:“Carbon Nanotubes: Present and Future

Commercial Applications ““Single-Wall Carbon Nanotubes”

“Carbon nanotube mass production: principles and processes”

“Fabrication and multifunctional properties of a hybrid laminate with aligned carbon nanotubes

grown in situ”

http://www.futuretimeline.net/subject/nanotechnology.htm



ABSTRACTCurrently CNT’s are used in specialty applications such as bikes, boats, and race cars because of CNT’s very light weight compared to competing high strength materials. Most recently CNT’s have been used in batteries, transistors, and even as a shield against space debris for NASA’s Juno spacecraft.

The increasing demand for CNT’s is driving advances in CNT synthesis, purification, and chemical modification technology. The advances in production are beginning to create new applications for CNT’s that go beyond the incorporation of bulk powders. The most promising areas of research are microelectronics, biotechnology, water purification, and composite materials.

http://www.sciencemag.org.lib-ezproxy.tamu.edu:2048/content/339/6119/535.full.pdf



IntroductionCarbon nanotubes• layers of carbon bonded in hexagonal lattices• form large sheets of graphene• when sheets are rolled up they form tubes which are existent

at a nanometer scale

Single Walled CNT

Multi Walled CNT

Length Less than 100nm up to several cm

Diameter .8-2nm 5-20nmL/D 100- 4x10^7 20-2x10^6

Thermal Conductivity

3500 W/mK(>diamond)

-

Tensile Strength - 100 GpaTwo types of CNTs• multi walled

• make incredibly strong fibers• single walled

• well suited for electrical and thermal conduction• the strength of a MWNT is ten times higher than any other known fiber!

http://4.bp.blogspot.com/JT5P-RJi06I/TF-lJcmNGmI/AAAAAAAAAFQ/ulIUwi-8lMc/s1600/CNT.gif

http://journalclubscienceblog.files.wordpress.com

/2012/07/multiwall-carbon-nanotube.jpg

Electron Structure of Nanotubes• Properties stem from “graphene”

• Conducting properties determined by nature of electronic states near Fermi energy- energy of highest occupied

electronic state at zero temperature

• Band structure• Unlike metal or

semiconductor• In between

• Most directions, electrons at Fermi energy are backscattered by atoms in the lattice

• Other directions, electrons that scatter from different atoms in lattice interfere destructively and suppresses backscattering• Only happens in y direction

and directions 60°, 120°, 180°, 240° from y

http://www.physics.umd.edu/condmat/mfuhrer/publications/PWorld00all.pdf


• Converting 2-D to 1-D forms tube• Resulting boundary conditions on wavefunction quantizes kn, component of k

perpendicular to axis of tube– kn =2πn/C

• Tube axis in y direction: tube acts as 1-D metal• Tube axis in different direction: semiconducting 1-D band structure

Electron Structure of Nanotubes


Converting from 2D to 1D • simply a matter of

changing the tube orientation

• usually done with an electrical current

If CNT is turned such that the axis is pointing in the metallic direction it results in a tube whose dispersion is a slice through the center of a cone. The reason it's called 1D at that point is because the fermi velocity is comparable to typical metals.


Nanotubes: how they conduct• Attach metal electrodes

– Can be connected to single tube or bundle of several hundred tubes– Drop tubes onto electrodes (a)– Deposit tubes on substrate, locate with scanning electron microscope,

attach leads to tubes using lithography (b)• Advanced techniques

– Growing tubes between electrodes– Attaching tubes to surface in controllable fashion using electrostatic or

chemical forces• Source and drain allow conducting properties to be measured

a b

http://www.physics.umd.edu/condmat/mfuhrer/publications/PWorld00all.pdfhttp://www.physics.umd.edu/condmat/mfuhrer/publications/PWorld00all.pdf



Nanotubes: how they conduct• Gate used to electrostatically induce carriers into tube

– Negative bias on gate induces positive charges on tube– Positive bias induces negative charges

• Conductance of tube measured as function of gate voltage



CNT Synthesis

Chemical vapor deposition• Most commonly used method of high volume CNT production• A catalyst is placed in a reactor and carbon containing gas is pumped

through at a specific temperature and pressure so that it forms graphene on the surface of the catalyst

Current bulk production methods• leave a large number of impurities and contaminants

• must be washed out with chemical treatments• can reduce CNT length and cause defects in CNT sidewalls

http://www.readcube.com/articles/10.1038/nnano.2009.67

http://www.readcube.com/articles/10.1038/nnano.2009.67

Chemical vapor deposition creates a bulk powder of CNT’s. Currently research is being done to find how catalyst and production conditions influence CNT chirality, diameter, length, and purity.

Product

Post Production Processing:High purity SWNT powders are created by separating bulk powder by density or gel chromatography. Following this various washes and thermal treatments are used to create stability on the CNT surface by addition of surfactants.

http://farm4.static.flickr.com/3186/3115816442_f5e050a423.

jpg?v=0

Separation of three proteins by gel chromatography. In the same way, CNT’s can be separated based on density.

Bulk CNT Powder

http://www.imb-jena.de/~rake/Bioinformatics_WEB/gifs/gel_filtration2.gif

10

CNT Production: Bottom-lineLaser Alignment• Using lasers, single walled carbon

nanotubes can be synthesized with large lengths, if this process can be scaled up then the cost of processing and purifying bulk powders to achieve desirable lengths could be avoided.

Self Aligning Growth• Synthesis of long CNT’s could be done

without expensive and time consuming liquid processing by coating substrates with catalyst particles which cause the CNT’s to line up together as they grow.

http://newsroom.unl.edu/releases/downloadables/photo/

20090225nanotubes.jpg

http://ars.els-cdn.com/content/image/1-s2.0-S0925400512002213-gr7.jpg

Composite Materials• Electrically conductive fillers in plastics• CNT powders mixed with polymers

– Increase stiffness, strength, toughness– No compromise in mechanical

properties• CNT resins

– Enhance fiber composites– Wind turbines, boat hulls




Composite Materials• MWNT added as flame retardant

additives to plastics– Change in rheology by nanotube

loading• Yarn

– High surface area increases strength when knotted




Work performed – CNT synthesis (MWNT)

• Use of Fluidized bed reactors for CVD– Allows for uniform gas diffusion– Allows for heat transfer to metal catalyst

nanoparticles• Has allowed for factors to greatly decrease

MWNT commercial prices– Scale-up– Use of low cost feed stocks– Increase in yields

http://en.wikipedia.org/wiki/File:Fluidized_Bed_Reactor_Graphic.svg



SWNT >> MWNT

Work performed – CNT synthesis (SWNT)

• SWNT synthesis by CVD requires – Separation according to chirality by density gradient

centrifugation + surfactant wrapping or gel chromatography– Stable CNT suspensions will require addition of surfactant– Washing or thermal treatment needed to remove surfactant– Very tight process control

http://cleanoceanaction.blogspot.com/2011/07/save-money-and-ocean.html

http://www.customtimberloghomes.com/log-home-cost-vs-timber-home-cost





Work performed – CNT synthesis• Synthesis of long, aligned CNTs

– Preferably without requiring to disperse in a liquid

http://www.elec.york.ac.uk/research/projects/Carbon_Nanotube_Growth_and_Characterization.html• Methods include

– Self-aligned growth of horizontal & vertical CNTS on substrates– Substrates are coated with catalyst particles

http://www.elec.york.ac.uk/research/projects/Carbon_Nanotube_Growth_and_Characterization.html

http://www.elec.york.ac.uk/research/projects/Carbon_Nanotube_Growth_and_Characterization.html

Work performed – CNT synthesis

• Can synthesize CNT forests and manipulate into

– Thin films– Intricate 3D microarchitectures– Directly spun into long yarns– Drawn into sheets

http://www.ornl.gov/info/ornlreview/v38_3_05/article11.shtml

http://www.imec.be/ScientificReport/SR2011/1414173.html





Work performed – Composite Materials

• To organize CNTs at a large scale, fiber composites are created by growing aligned CNT forests on

– Glass– SiC– Alumina– Carbon Fibers

• Creates fuzzy fibers• Improves toughness by more than 50%

http://cosmiclog.nbcnews.com/_nv/more/section/archive?year=2011&month=1&ct=a&pc=25&sp=25



Work performed – Coating and Films

• CNT can be a multifunctional coating material– Leveraging CNT dispersion– Functionalization– Large-area deposition techniques

• Example:– MWNT containing paints reduce bio-fouling on hulls– Anticorrosion coating on metals while providing

stiffness and strength

http://marinesupplydock.wordpress.com/2012/10/25/a-winterization-guide-for-boats/




• CNT-based transparent conducting films– Alternative to expensive indium tin oxide (ITO)– Flexible, and not brittle– Application in

• Displays• Touch screen devices• photovolatics

http://en.wikipedia.org/wiki/File:Samsung_flexible_AMOLED_phone.jpg




• CNT conductors can be deposited from solution– Slot-die coating– Ultrasonic spraying

• Can be patterned by economic nonlithographic methods• Recent developments have allowed for

– SWNT films with 90% transparency– Sheet resistivity of 100 ohm per square– Adequate applications such as CNT thin-film heaters like defrosting windows or

sidewalks

http://funnypicturesplus.com/defrosting-car-window.html



Work performed – Microelectronics

• SWNTs are attractive for transistors due to– Low electron scattering– Band-gap

• Depends on diameter• Depends on chiral angle

• Also compatible with field-effect transistor (FET) architectures and high k-dielectrics.– Current densities achieved were greater than

those obtained for Si devices.

http://www.circuitstoday.com/fet-field-effect-transistors-introduction




• CNT arrays containing 10-103 SWNTs in patterned films increases– Output current– Compensates for defects and chirality

differences– Improves device uniformity and reproducibility– Up to 105 CNTs on a single chip

http://www.nanotech-now.com/news.cgi?story_id=06788




• CNT thin film transistors (TFT) appealing for organic light emitting diodes (OLED) displays

– Higher mobility than amorphous Si

– Can be deposited at low T, and non-vacuum methods

http://http://www.charterworld.com/news/new-sony-flexible-oled-display-rollable-around-a-pencil-to-have-applications-in-the-superyacht-industry/oled-display

http://www.sciencemag.org/content/339/6119/535/F3.large.jpg

http://www.charterworld.com/news/new-sony-flexible-oled-display-rollable-around-a-pencil-to-have-applications-in-the-superyacht-industry/oled-display






• CNTs can be used in high-power amplifiers and function as both– Electric leads– Heat dissipaters


• CNTs can replace Cu in microelectronic interconnects. – Low scatter– High current carrying capacity– Resistance to electromigration



Work performed – Energy Storage

• Use of MWNTs in Li-ion batteries– Laptop notebooks– Mobile phones

• MWNT powder blended with active materials– Increases electrical connectivity– Increases mechanical strength– Enhances cycle life and rate

capability

http://metaefficient.com/computers/the-greenest-notebook-computers-of-2008.html



Work performed – Energy Storage (supercapacitors)

• Study on packaged cells utilizing forest-grown SWNTs revealed remarkable performance

– 16 Wh kg-1 energy density– 10 kW kg-1 power density– 16 year lifetime forecast

• The only drawback is the high cost of SWNTs




Work performed – Energy Storage (Fuel Cells)

• Use of CNTs in fuel cells as catalyst

• Reduce Pt usage by 60%• For organic solar cells, CNTs

– Reduce undesired carrier recombination– Enhance resistance to photo-oxidation




Work performed – Environment (Water filters)

• Application of tangled CNT sheets to provide robust networks that have controlled nanoscale porosity and are robust– Mechanically – Electrochemically

• Used to electrochemically oxidize organic contaminants, viruses, and bacteria

• Enhanced permeability will enable lower energy cost for water desalination




Work performed – Biotechnology

• CNTs have been investigated as components of– Biosensors – Medical devices

• Appeal due to compatibility with biomolecules (DNA/proteins) from two aspects: – Dimensional – chemical

http://convergence.ucsb.edu/news/ultra-sensitive-electrical-biosensor-unlocks-potential-instant-diagnostic-devices




Work performed – Biotechnology

• CNTs enable biological functions like

– Fluoroscence– Photoacoustic imaging– Localized heating via near-infrared radiation

http://en.wikipedia.org/wiki/File:FluorescentCells.jpg

http://en.wikipedia.org/wiki/File:FluorescentCells.jpg

Work performed – Biotechnology (SWNT

biosensors)• Adsorption of target molecules on CNT surface allow for large changes in• Electrical impedance• Optical properties

• Application include• Gas and toxin detection in industry

and military• Test strips for hormones and

biological markers (NO2,troponin, estrogen, progesterone)

http://bme240.eng.uci.edu/students/08s/jentel/Diagnose-hereditary-disease.htm



Work performed – Biotechnology (In vivo)

• CNT can be loaded with cargo on walls or inside tube

• Attaches to cell membrane

• Release cargo upon near-infrared radiation

http://thepluripotent.com/?tag=cirm

http://thepluripotent.com/?tag=cirm

Nanotube transistors• Semiconducting nanotubes• Tube turned on: negative bias to gate

– Induces holes on tube– Makes conductive

• Tube turned off: positive bias to gate– Depletes holes– Decreases conductance

• Resistance of off state can be more than million times greater than on state– similar to p-type metal-oxide-silicon field effect transistor



Nanotube transistors• Conductance limited by barriers that holes see as they traverse tube

– Barriers caused by • structural defects in tube• Atoms absorbed on tube• Localized charges near tube

• Holes see peaks and valleys that they must hop through if tube is to conduct• Resistance dominated by highest barriers



Nanotubes as one-dimensional metals

• Have large number of carriers• Conductance much larger than

semiconducting nanotubes• Conductance oscillates as

function of gate voltage– Oscillations occur when

additional electron is added to nanotube

– Regular and periodic oscillations: electronic states extended along entire length of tube

• Electrons can travel long distances in nanotubes without being backscattered



Nanotubes as one-dimensional metals

• 1-D conductor at low voltage makes it ideal system to test ideas about electrons• 1-D repulsive Coulomb interactions between neighboring electrons should behave

differently than 2-D or 3-D• 2-D/3-D (a)

– Behaves as Fermi Liquid– Electrons fill low energy states up to Fermi energy– Low energy excitations act like free electrons (can tunnel without difficulty)

• 1-D (b)– Low energy excitations are collective excitations of entire electron system



New Devices and Geometries

• Crossing metallic and semiconducting tube– Metallic tube locally depletes holes in

semiconducting tube– Electron travelling tube must overcome barrier– Applying voltage at one end of tube leads to

correction at that end but not other• Nanotube coils

– Individual tube loops back on itself to form ring-like structure

– Used as solenoids to create magnetic fields or study quantum interference phenomena



Future Works• Investigate why yarns and sheets have thermal, electrical, and

mechanical properties that are significantly lower than individual CNT.

http://www.fastcompany.com/3000082/creating-artificial-muscles-more-powerful-anything-nature

http://www.gaia3d.co.uk/3d-models/3d-chemistry/carbon-nanotube/





Future Works• Better understand CVP process condition

– Reduce contaminants– Avoid costly thermal annealing and chemical treatments

http://www.made-in-zelenograd.com/products/mvu-tm-izophase-cvd-icp/



Future Works• Better understand how CVP process conditions effect

– Chirality– Diameter– Length– Purity

http://drugdeliverysystems.webs.com/nanotubes.htm



Future Works• Further price reductions of SWNT needed• Commercial application of SWNT is emerging• Applications require chiral-specific SWNTs• Synthesize long aligned CNTs without the need to disperse in a liquid

http://nextbigfuture.com/2010/11/emerging-applications-of-carbon.html http://drugdeliverysystems.webs.com/nanotubes.htm

http://nextbigfuture.com/2010/11/emerging-applications-of-carbon.html



Future Works• Improve resistivity of transparent SWNT films so that they are

better than equally transparent, optimally doped ITO coatings.

http://www.tradekorea.com/products/ito_coating_glass.html

http://onlinelibrary.wiley.com/doi/10.1002/smll.201201398/abstract





Future Works• Difficult control of CNT

– Diameter– Chirality– Density– placement

• Introduces difficulty to control microelectronic production over large areas. • Required improved understanding of CNT surface chemistry for better

commercialization of CNT TFT

http://www.mikroe.com/old/books/keu/04.htm



Future Works• CNT biotoxicity

– Must control CNT retention within body– Prevent undesirable accumulation

• Better understand surface chemistry and geometry• Medical application requires better understanding of interaction of CNT with the

immune system• Develop exposure standards for

– Inhalation– Ingestion– Skin contact– Injection

http://hyperphysics.phy-astr.gsu.edu/hbase/biology/celmem.html



ConclusionsBiotechnolo

gy

Environment

Energy storage

Microelectronics

Coating

Films

http://4.bp.blogspot.com/_JT5P-RJi06I/TF-lJcmNGmI/AAAAAAAAAFQ/ulIUwi-8lMc/s1600/CNT.gif

Water filtersTransistorsBiosensors

screens

http://4.bp.blogspot.com/_

http://4.bp.blogspot.com/_JT5P-RJi06I/TF-lJcmNGmI/AAAAAAAAAFQ/ulIUwi-8lMc/s1600/CNT.gif

References1. M.F.L De Volder, S.H. Tawfick, R.H. Baughman, A.J Hart,

Carbon Nanotubes: Present and Future Commercial Applications. Science 339, 6119 (2013)

2. P.L McEuen, Single-wall carbon nanotubes. Physics World 13, 6 (2000).

3. Q. Zhang, J.-Q. Huang, M.-Q. Zhao, W.-Z. Qian, F. Wei, Carbon nanotube mass production: principles and processes. ChemSusChem 4, 864 (2011).

4. E. J. Garcia, B. L. Wardle, A. J. Hart, N. Yamamoto, Fabrication and multifunctional properties of a hybrid laminate with aligned carbon nanotubes grown In Situ. Compos. Sci. Technol. 68, 2034 (2008).

http://research.che.tamu.edu/groups/Seminario/index-1.html



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