Carbon Nanotubes (CNTs)

Class: Material Science Engineering Student : Hoang Van Hanoi Tien -2012 DID YOU KNOW?  Carbon nanotubes, composed of interlocking carbon atoms, are 1000x thinner than an average human hair – but can be 200x stronger than steel outline  Definition  Theory and properties  Synthesis  Potential and current applications  Challenges and future What are carbon nanotubes CNT: Rolling-up a graphene sheet to form a tube Schematic of a CNT STM image of CNT  Carbon nanotubes are hexagonally shaped arrangements of carbon atoms that have been rolled into tubes  These tiny straw-like cylinders of pure carbon have useful electrical propeties They have already been used to make tiny transistor and one-dimentional copper wire Types of CNTs  Single Wall CNT (SWCNT)  Multiple Wall CNT (MWCNT)  Can be metallic or semiconducting depending on their geometry Single- walled -Most single-walled nanotubes (SWNTs) have a diameter of cloes to nanometer,with a tube length that can be many millions of time longer -The structure of a SWNTs can be conceptualized by wrapping a one-atomthick layer of graphite called graphene in to a seamless cylender If: m=0 , the nanotubes are called zigzag n=m ,the nanotubes are called armchair Otherwise ,they are called chiral Multi-walled  Multi-walled nanotubes (MWNTs) consist of multiple rolled layer( concentric tubes) of graphene Triple-walled armchair CNTs  In the Russian Doll model, sheets of graphite are arranged in concentric cylinders, e.g., a (0,8) singlewalled nanotube (SWNT) within a larger (0,17) singlewalled nanotube  In the Parchment model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper  The interlayer distance in multi-walled nanotubes is close to the distance between graphene layers in graphite, approximately 3.4 Å The Russian Doll structure is observed more commonly Its individual shells can be described as SWNTs, which can be metallic or semiconducting Laser-assisted thermal chemical vapour deposition the growth mechanism  Sources of laser:a medium power, continuous wave CO laser,perpendicularonto a substrate,  pyrolyses sensitised mixtures of Fe(CO) vapour and acetylene in a flow reactor  Catalyst: Fe (very small iron particles)  Substrate: sillica iron pentacarbonyl vapour, +ethylene +acetylene single- and multiwalled carbon nanotubes Purification  The main impurities :graphite (wrapped up) sheets, amorphous carbon, metal catalyst and the smaller fullerenes…  Rules : -separate the SWNTs from the impurities - give a more homogeneous diameter or size distribution  The techniques that will be discussed are oxidation, acid treatment, annealing, ultrasonication, micro filtration, ferromagnetic separation, cutting, functionalisation and chromatography techniques applications Nanotubes are rolled-up graphene sheets, and graphene is one of the stiffest materials when subjected to deformations parallel to the sheet ⇒nanotubes show exceptional mechanical properties, especially a high strength-to-weight ratio Applications:  Field emission  Nanotube sensors  Nanotube transistors  Nanotubes as SPM tips  Energy Storage  Conductive Adhesives and Connectors  Biomedical Applications……… Schematics of a nanotube transistor, with some measurements Use of a MWNT as AFM tip VGCF stands for Vapour Grown Carbon Fibre At the centre of this fibre the MWNT forms the tip.the VGCG provides a convenient and robust technique for mounting the MWNT probe for use in a scanning probe instrustment Space elevator Faster computer chips cancer treatment  Use carbon nanotubes as drug delivery tools Challenges and potentials  Potentials :  the new wonder material, can useful in many types of industry ,especially in electronics applications  The field of research for CNTs has become so broad over the past 20 years that they are being tested for use in fields  Challenges :  Too expensive (~ $ 200per gram)  toxicological issues  hard to purification and the ability to manipulate structures at the atomic scale… summary  Carbon nanotubes have very different properties compared to the other carbon allotropes - these unique properties offer huge potential in product development  Nanomaterials, particularly carbon nanotubes (CNTs), hold great promise for a variety of industrial, consumer, and biomedical applications, due to their outstanding and novel properties sources D.A.Bochvar and E.G.Gal'pern, Dokl.Akad.Nauk.USSR, 209, (610, 1973 ) 2.http://www.ou.edu/engineering/nanotube, 2003 http://nanotube.msu.edu/ 4.http://www.pa.msu.edu/cmp/csc/nanotube.htm5 5.http://en.wikipedia.org/wiki/Carbon_nanotube http://students.chem.tue.nl/carbonnanotubes/ap plications.html ……… [...]... fullerenes and carbon nanotubes Extreme carbon nanotubes -The observation of the longest carbon nanotubes (18.5 cm long) was reported in 2009 These nanotubes were grown on Si substrates using an improved chemical vapor deposition (CVD) method and represent electrically uniform arrays of single-walled carbon nanotubes -The shortest carbon nanotube is the organic compound cycloparaphenylene -The thinnest carbon. .. was grown inside a multi-walled carbon nanotube -The thinnest freestanding single-walled carbon nanotube is about 4.3 Å in diameter PROPERTIES OF CARBON NANOTUBES Strength and elasticity  CNTs are expected to be the ultimate high-strength filber  Single wall carbon nanotubes are stiffer than steel and are very resistant to damage from physical forces  Carbon Nanotubes (CNTs) very useful as probe tips... very high-resolution scanning probe microscopy elasticity -The current Young’s modulus value of single walled carbon nanotubes is about 1 terapascal -The modulus of the multi walled carbon nanotubes correlates to the amount of disorder in the carbon nanotube walls -when multi walled carbon nanotubes break, the outermost layers break first Comparison of mechanical properties Materials Young’modulus(Tpa)... as carbon nanotube bent into a torus (doughnut shape) -Nanotorus are predicted to have many unique properties such as : +magnetic moments +thermal stability … -Vary widely depending on radius of the torus and the radius of the tube nanobud  In nanotechnology ,carbon nanobuds form a material (discovered and synthesized in 2006) which combines two previously discovered allotropes of carbon: carbon nanotubes. .. Techniques have been developed to produce carbon nanotubes in sizeable quanlities ,some of them are: - Arc discharge - Laser ablation - Chemical vapor deposition(CVD) Arc discharge  Nanotubes were observed in 1991 in the carbon soot of graphite electrodes during an arc discharge, by using a current of 100 amps , that was intended to produce fullerenes  the carbon contained in the negative electrode... process gas (such as ammonia , nitrogen or hydrogen ) and a carboncontaining gas (such as acetylene , ethylene , ethanol or methane ) > >Nanotubes grow at the sites of the metal catalyst; the carbon- containing gas is broken apart at the surface of the catalyst particle, and the carbon is transported to the edges of the particle, where it forms the nanotubes Laser-assisted thermal chemical vapour deposition... and multi-walled nanotubes with lengths of up to 50 micrometers with few structural defects Laser ablation  a pulsed laser vaporizes a graphite target in a high- temperature reactor while an inert gas is bled into the chamber  Nanotubes develop on the cooler surfaces of the reactor as the vaporized carbon condenses  A water-cooled surface may be included in the system to collect the nanotubes  The... of Fe(CO) 5 vapour and acetylene in a flow reactor  Catalyst: Fe (very small iron particles)  Substrate: sillica iron pentacarbonyl vapour, +ethylene +acetylene single- and multiwalled carbon nanotubes Purification  The main impurities :graphite (wrapped up) sheets, amorphous carbon, metal catalyst and the smaller fullerenes…  Rules : -separate the SWNTs from the impurities - give a more homogeneous... Toxicity  Under some conditions ,nanotubes can cross membrane barriers ,which suggests that if raw materials reach the organs, they can include harmful effects such as inflammatory and fibrotic reactions  CNTs were capable of producing inflammation, epithelioid granulomas (microscopic nodules), fibrosis, and biochemical/toxicological changes in the lungs  =>> >carbon nanotubes can pose a serious risk... functionalisation and chromatography techniques applications Nanotubes are rolled-up graphene sheets, and graphene is one of the stiffest materials when subjected to deformations parallel to the sheet nanotubes show exceptional mechanical properties, especially a high strength-to-weight ratio Applications:  Field emission  Nanotube sensors  Nanotube transistors  Nanotubes as SPM tips  Energy Storage  Conductive ... properties of both fullerenes and carbon nanotubes Extreme carbon nanotubes -The observation of the longest carbon nanotubes (18.5 cm long) was reported in 2009 These nanotubes were grown on Si substrates... walled carbon nanotubes is about terapascal -The modulus of the multi walled carbon nanotubes correlates to the amount of disorder in the carbon nanotube walls -when multi walled carbon nanotubes. .. ultimate high-strength filber  Single wall carbon nanotubes are stiffer than steel and are very resistant to damage from physical forces  Carbon Nanotubes (CNTs) very useful as probe tips for very