CARBON NANOTUBES AND THEIR APPLICATIONS-1-print

[Virtual Presenter] CARBON NANOTUBES AND THEIR APPLICATIONS MAHAMOOD ALI K K B200421CH CHED.

[Audio] OUTLINE Introduction History & Discovery Types of Carbon nanotubes SYNTHESIS OF CARBON NANOTUBES PROPERTIES OF CNTs APPLICATION OF CARBON NANOTUBES CHALLENGES CONCLUSION REFERENCE.

[Audio] Introduction Carbon nanotubes (CNTs) are allotrope of Carbon with a cylindrical nanostructure. Carbon nanotubes (CNTs) are best described as a seamless cylindrical hollow fibers, comprised of a single sheet of pure graphite (Graphene), having a diameter of 0.7 to 50 nanometers with lengths generally in the range of 10-100 of microns. Carbon nanotubes (CNTs) are made by rolling up of sheet of GRAPHENE into a cylinder..

[Audio] Graphene Graphene is basically a 2D single layer of graphite. Graphene is stronger and stiffer than diamond. It, however, can be stretched like rubber. The C–C bond(??2) length in graphene is ~0.142 nm. The graphene sheets stack to form graphite with an inter planar spacing of 0.335 nm Roll-up Graphene Carbon Nano Tubes.

[Audio] History & Discovery In 1991, Japanese scientist SUMIO IIJIMA NEC Laboratory in Tsukuba found an extremely thin needle-like material when examining carbon materials under an electron microscope. He named these materials "carbon nanotubes" since then name has been widely accepted..

[Audio] Types of Carbon nanotubes  The structure of a carbon nanotube is formed by a layer of carbon atoms that are bonded together in a hexagonal (honeycomb) mesh. This one-atom thick layer of carbon is called graphene, and it is wrapped in the shape of a cylinder and bonded together to form a carbon nanotube.  Nanotubes can have a single outer wall of carbon, or they can be made of multiple walls (cylinders inside other cylinders of carbon). Accordingly they are called: – Single-walled carbon nanotube – Multi-walled carbon nanotube.

[Audio] Single-walled Nanotubes(SWNTS) A single-walled carbon nanotube (SWNT) may be thought of as a single atomic layer thick sheet of graphene rolled into a seamless cylinder. Most single-walled nanotubes (SWNT) have a diameter of close to 3 nanometer, with a tube length that can be many 10^4 times longer. It requires catalyst for their synthesis.

[Audio] The structure of a single-wall carbon nanotube is specified by the vector called "Chiral vector" Depending on the chiral indices (?1 ,?2) and chiral angle(ɵ) SWCNT can be – i. Zig-Zag (ɵ = 0) ii. Arm Chair (ɵ=30) iii. Chiral (0<ɵ<30)  Depending upon their different structures, CNTs can exhibit metallic or semiconducting properties..

[Audio] Multi-walled Nanotubes (MWNTs) Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphite. MWCNTs can have OD ~ 20nm, ID ~ 3nm length can be 10^4 times longer. It can be produced without catalyst.  Purity of product is high. There are two structural models of multi-walled nanotubes: – Russian Doll model – Parchment model.

[Audio] In the Russian Doll model, a carbon nanotube contains another nanotube inside it (the inner nanotube has a smaller diameter than the outer nanotube). In the Parchment model, a single graphene sheet is rolled around itself multiple times, resembling a rolled up scroll of paper..

[Audio] SYNTHESIS OF CARBON NANOTUBES Arc Discharge Method (1991) Laser Ablation (1995) Chemical Vapor Deposition (CVD)(1993).

[Audio] Arc Discharge method This method successfully used to synthesize CNTs in small quantities Opposing anode and cathode terminals made of 6-mm and 9-mm graphite rods respectively are placed in an inert environment (He or Ar at ~500 Torr). A strong current, typically around 100 A (DC or AC), is passed between the terminals generating arc-induced plasma that evaporates the carbon atoms in the graphite. The nanotubes grow from the surface of these terminals. A catalyst can be introduced into the graphite terminal..

[Audio] Although MWNTs can be formed without a catalyst, it has been found that SWNTs can only be formed with the use of a metal catalyst such as iron or cobalt..

[Audio] Laser Ablation Starting material is graphite with traces of Co and Ni that act as nucleation sites in formation of nanotubes Graphite work piece is placed in quartz tube filled with argon and heated to 1200°C A pulsed laser beam is focused on surface, causing carbon atoms to evaporate from the bulk graphite Argon moves carbon atoms to cool copper surface, where they condense, forming nanotubes with diameters 10 to 20 nm and lengths ~ 100 nm.

[Audio] Chemical Vapor Deposition (CVD) CVD has the highest potential for mass production of carbon nanotubes. It can produce bulk amounts of defect-free CNTs at relatively low temperatures..

[Audio] Starting material is hydrocarbon gas such as methane (CH4 ) Gas is heated to 1100°C, causing it to decompose and release carbon atoms Atoms condense on cool substrate to form nanotubes Substrate surface may contain metallic traces that act as nucleation sites for nanotubes CVD process can be operated continuously, making it attractive for mass production.

[Audio] Mechanical and Physical Electrical and Electronics Properties Thermal Properties PROPERTIES OF CNTs.

[Audio] Mechanical and Physical Properties Strength Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp2 bonds formed between the individual carbon atoms which are stronger than 3D diamond bonds..

[Audio] Hardness Standards single-walled carbon nanotubes can withstand a pressure up to 25 GPa without deformation. The bulk modulus of superhard phase nanotubes is 462 to 546 GPa, even higher than that of diamond (420 GPa for single diamond crystal)..

[Audio] Electrical properties Behaviors According to Structure Chiral Vector If ?1= ?2 the nanotube is metallic If (n1-n2) is a multiple of 3, then the nanotube is semiconducting with a very small band gap, otherwise the nanotube is a moderate semiconductor. Semiconducting and Doping Piezoresistance Photoconductivity of Carbon Nanotubes ?h= ?1?1 + ?2?2.

[Audio] Thermal Properties The thermal properties of carbon nanotubes are directly related to their unique structure and small size Specific Heat Thermal conductivity.

[Audio] APPLICATION OF CARBON NANOTUBES Electronic Applications of Carbon Nanotubes CNTs in Mechanical Field CNT in Medicine Other applications of CNTs.

[Audio] Electronic Applications of Carbon Nanotubes Conductive Composites Electron Emitters Nanoprobes Sensors Biomedical Industry Automotive Industry Food Industry Environmental Monitoring FED Display  Template.

[Audio] CNTs in Mechanical Field CNT Based Actuator High technology applications, including humanoid robots, artificial and damaged hearts, artificial limbs, medical prosthetic devices etc CNT Based Composites Polymer matrix composite Ceramic matrix composite.

[Audio] CNT in Medical CNTs in Drug Delivery and Cancer Therapy CNTs as Biosensors CNT Network Bio-Stress Sensors Glucose detection biosensors DNA detection biosensors.

[Audio] Other applications of CNTs CNTs Thermal Materials CNTs Air and Water Filtration Hydrogen Storage Energy Storage Li ion battery.

[Audio] CHALLENGES Despite all the research, scientists still don't fully understand exactly how they work. Extremely small, so are difficult to work with. Currently, the process is relatively expensive to produce the nanotubes. Level of purity is less in most of the synthesis techniques. Challenge is in the manipulation of nanotubes..

[Audio] CONCLUSION Their phenomenal mechanical properties, and unique electronic properties make them both interesting as well as potentially useful in future technologies. Nanotechnology is predicted to spark a series of industrial revolutions in the next two decades that will transform our lives to a far greater extent than silicon microelectronics did in the 20th century. Lack of commercially feasible synthesis and purification methods is the main reason that carbon nanotubes are still not widely used nowadays..

[Audio] REFERENCE  "Carbon Nanotubes: Properties and Applications" Edited by Michael J. O'Connell, Ph.D. Senior Research Scientist, Theranos, Inc. Menlo Park, California.  "Electrical properties of Carbon Nanotubes" Kasper GroveRasmussen Thomas Jorgensen, August 28, 2000.  "Mechanical properties of carbon nanotubes: theoretical predictions and experimental measurements" Rodney S. Ruoff a, Dong Qian , Wing Kam Liu.  "Thermal properties of carbon nanotubes and nanotube-based materials", J. Hone1, M.C. Llaguno, M.J. Biercuk, A.T. Johnson, B. Batlogg, Z. Benes, J.E. Fischer.  "Carbon Nanotube-Based Sensors" Niraj Sinha, Jiazhi Ma, and John T. W. Yeow.

[Audio] THANK YOU. THANK YOU.