Carbon Nanotubes: The exciting future of fullerenes Presented 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/nanotechn ology.htm
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Carbon Nanotubes: The exciting future of fullerenes
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Carbon Nanotubes:The exciting future of
fullerenesPresented By:• David Chaar• Steven Hering• Phillip Thane• Kori Mondin
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.
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!
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
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
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
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.
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.
• 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
• 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
• 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
• 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
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
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).