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UNIVERSITY OF ENGINEERING AND MANAGEMENT,JAIPUR,RAJASTHAN
TOPIC: NANO TUBES
BRANCH ECE
* SOUDIP SINHA ROY .
.
CARBON NANOTUBES
DAVID MCDERMOTT
JAKE BORRAJO
PHYS43 MODERN PHYSICS, SRJC
SECTION 5756
INSTRUCTOR: DR. YOUNES ATAIIYAN
MODERN PHYSICS PROJECT
WHAT ARE CARBON NANOTUBES.
•CARBON NANOTUBES (CNTS) ARE ALLOTROPES OF CARBON. THESE
CYLINDRICAL CARBON MOLECULES HAVE INTERESTING PROPERTIES THAT MAKE THEM POTENTIALLY USEFUL IN MANY APPLICATIONS IN NANOTECHNOLOGY,
ELECTRONICS, OPTICS AND OTHER FIELDS OF MATERIALS SCIENCE, AS WELL AS
POTENTIAL USES IN ARCHITECTURAL FIELDS. THEY EXHIBIT EXTRAORDINARY STRENGTH AND UNIQUE ELECTRICAL PROPERTIES, AND
ARE EFFICIENT CONDUCTORS OF HEAT. THEIR FINAL USAGE, HOWEVER, MAY BE LIMITED BY THEIR POTENTIAL TOXICITY.
HOW CNTS ARE MADE
• ARC DISCHARGE
• CNTS CAN BE FOUND IN THE CARBON SOOT OF GRAPHITE ELECTRODES DURING AN ARC DISCHARGE INVOLVING HIGH CURRENT. THIS PROCESS YIELDS CNTS WITH LENGTHS UP TO 50 MICRONS.
• LASER ABLATION
• IN THE LASER ABLATION PROCESS, A PULSED LASER VAPORIZES A GRAPHITE TARGET IN A HIGH-TEMPERATURE REACTOR WHILE AN INERT GAS IS INSERTED INTO THE REACTOR. NANOTUBES DEVELOP ON THE COOLER SURFACES OF THE REACTOR AS THE VAPORIZED CARBON CONDENSES.
• OTHER METHODS WHERE CNTS ARE CREATED:
- CHEMICAL VAPOR DECOMPOSITION
- NATURAL, INCIDENTAL, AND CONTROLLED FLAME ENVIRONMENTS
STRENGTH PROPERTIES• CARBON NANOTUBES HAVE THE STRONGEST TENSILE
STRENGTH OF ANY MATERIAL KNOWN.
• IT ALSO HAS THE HIGHEST MODULUS OF ELASTICITY.
MaterialYoung's Modulus (TPa)
Tensile Strength (GPa)
Elongation at Break (%)
SWNT~1 (from 1 to
5)13-53E 16
Armchair SWNT
0.94T 126.2T 23.1
Zigzag SWNT 0.94T 94.5T 15.6-17.5
Chiral SWNT 0.92
MWNT 0.8-0.9E 150
Stainless Steel
~0.2 ~0.65-1 15-50
Kevlar ~0.15 ~3.5 ~2
ELECTRICAL PROPERTIES
• IF THE NANOTUBE STRUCTURE IS ARMCHAIR THEN THE ELECTRICAL PROPERTIES ARE METALLIC
• IF THE NANOTUBE STRUCTURE IS CHIRAL THEN THE ELECTRICAL PROPERTIES CAN BE EITHER SEMICONDUCTING WITH A VERY SMALL BAND GAP, OTHERWISE THE NANOTUBE IS A MODERATE SEMICONDUCTOR
• IN THEORY, METALLIC NANOTUBES CAN CARRY AN ELECTRICAL CURRENT DENSITY OF 4×109
A/CM2 WHICH IS MORE THAN 1,000 TIMES GREATER THAN METALS SUCH AS COPPER
THERMAL PROPERTIES• ALL NANOTUBES ARE EXPECTED TO BE VERY GOOD THERMAL
CONDUCTORS ALONG THE TUBE, BUT GOOD INSULATORS
LATERALLY TO THE TUBE AXIS.
• IT IS PREDICTED THAT CARBON NANOTUBES WILL BE ABLE TO
TRANSMIT UP TO 6000 WATTS PER METER PER KELVIN AT ROOM
TEMPERATURE; COMPARE THIS TO COPPER, A METAL WELL-
KNOWN FOR ITS GOOD THERMAL CONDUCTIVITY, WHICH
TRANSMITS 385 WATTS PER METER PER K.
• THE TEMPERATURE STABILITY OF CARBON NANOTUBES IS
ESTIMATED TO BE UP TO 2800OC IN VACUUM AND ABOUT 750OC
IN AIR.
DEFECTS
• DEFECTS CAN OCCUR IN THE FORM OF ATOMIC
VACANCIES. HIGH LEVELS OF SUCH DEFECTS CAN
LOWER THE TENSILE STRENGTH BY UP TO 85%.
• BECAUSE OF THE VERY SMALL STRUCTURE OF
CNTS, THE TENSILE STRENGTH OF THE TUBE IS
DEPENDENT ON ITS WEAKEST SEGMENT IN A
SIMILAR MANNER TO A CHAIN, WHERE THE
STRENGTH OF THE WEAKEST LINK BECOMES THE
MAXIMUM STRENGTH OF THE CHAIN.
ONE-DIMENSIONAL TRANSPORT• DUE TO THEIR NANOSCALE DIMENSIONS, ELECTRON
TRANSPORT IN CARBON NANOTUBES WILL TAKE
PLACE THROUGH QUANTUM EFFECTS AND WILL
ONLY PROPAGATE ALONG THE AXIS OF THE TUBE.
BECAUSE OF THIS SPECIAL TRANSPORT PROPERTY,
CARBON NANOTUBES ARE FREQUENTLY REFERRED
TO AS “ONE-DIMENSIONAL.”
APPLICATIONS
• NANOTUBES HOLD THE PROMISE OF CREATING NOVEL
DEVICES, SUCH AS CARBON-BASED SINGLE-ELECTRON
TRANSISTORS, THAT SIGNIFICANTLY SMALLER THAN
CONVENTIONAL TRANSISTORS.
QUANTUM COMPUTING• NANOTUBES AND OTHER FULLERENES CAN BE FILLED WITH
MOLECULES THAT HAVE EITHER AN ELECTRONIC OR
STRUCTURAL PROPERTY WHICH CAN BE USED TO REPRESENT
THE QUANTUM BIT (QUBIT) OF INFORMATION, AND WHICH
CAN BE ASSOCIATED WITH OTHER ADJACENT QUBITS.
HEALTH HAZARDS
• ACCORDING TO SCIENTISTS AT THE NATIONAL INSTITUTE OF
STANDARDS AND TECHNOLOGY, CARBON NANOTUBES
SHORTER THAN ABOUT 200 NANOMETERS READILY ENTER
INTO HUMAN LUNG CELLS SIMILAR TO THE WAY ASBESTOS
DOES, AND MAY POSE AN INCREASED RISK TO HEALTH.
• CARBON NANOTUBES ALONG WITH THE MAJORITY OF
NANOTECHNOLOGY, ARE AN UNEXPLORED MATTER, AND
MANY OF THE POSSIBLE HEALTH HAZARDS ARE STILL
UNKNOWN.
Scientists used to think know everything about this element, and since it was not in great
demand in industry boron was out of the focus of attention.
But in recent decades, boron and its compounds has found application in different
industries such as atomic, rocket-building, metal processing, chemical and many others.
Boron atoms are capable of forming both ion and covalent bonds. They can make
chains, frames, nets etc. Still, we do not know much about this element.
Boron has found application in many fields of modern technology.
small addition of boron to steel (0,0005…0,005 %) increase its hardness!
Boron better than any other element removes gases from copper that improve its
properties.
Saturation of metals with boron forms hard borids!
«We need to know much to understand how
little we know»
THERE IS NO CONSENSUS ABOUT HOW MANY BORON MODIFICATIONS EXIST.
• RESEARCHERS (BORIS
YAKOBSON) ANTICIPATED THE
EXISTENCE OF A FULLERENE
CONSISTING OF 80 BORON
ATOMS.
• BORON NANOTUBES WERE
SYNTHESISED RECENTLY AND
THEIR PROPERTIES AND NATURE
HAVE NOT BEEN FULLY
REVEALED.
__________________________________________________________________________________________________
ONE OF THE CONFIGURATIONS OF BORON –HEXAGONAL BORON
FIG. 1.BORON STRUCTURE.• TABLE 1. MAIN PROPERTIES OF QUASI-
PLANAR HEXAGONAL BORON.
The number of atoms в EEC
Atom charge Ionazation potential, eV
64 07.31
80 07.25
88 07.95
96 08.08
108 08.13
BY ANALOGY WITH CARBON NANOTUBES WE ASSUMED THAT BORON NANOTUBES CAN BECONSTRUCTED BY ROLLING OF HEXAGONAL
QUASI-PLANAR BORON
DUE TO THREE-CENTER BONDING
BORON NANOTUBES ARE MAINLY OF
TRIANGULAR AND HEXAGONAL TYPES.
BORON NANO TUBES WITH DEFECTS
BORON NANOTUBE WITH SUBSTITUTION DEFECTS (EITHER NEUTRAL CARBON ATOM (С), OR POSITIVELY (С+) AND NEGATIVELY (С–) CHARGED CARBON IONS)
SORPTION PROPERTIES OF BORON NANOTUBES
• IT IS KNOWN THAT BORON NANOTUBES HAVE
UNIQUE SOPTION PROPERTIES. MUCH
RESEARCH INTO THE MECHANISM OF ATOM
AND MOLECULAR ADSORPTION ON THEIR
SURFACE HAS BEEN CARRIED OUT.
• THE STUDY OF THE SURFACE STRUCTURE
HYDROGENATION IS PROMISING FOR ITS
APPLICATION AS A STORAGE FOR
MOLECULAR HYDROGEN.
• THE SEARCH FOR STRUCTURES WITH WELL-
DEVELOPED SURFACES CAPABLE OF
ADSORBING GASES (INCLUDING HYDROGEN)
REMAINS IN THE FOCUS OF ATTENTION. IN
THIS RESPECT RESEARCH OF SORPTION
PROPERTIES OF BORON NANOTUBES IS
IMPORTANT.
______________________________________________
REFERENCES• HTTP://WWW.NEWS-MEDICAL.NET/NEWS/22799.ASPX
• CHAE, H.G.; KUMAR, S. (2006). "RIGID ROD POLYMERIC FIBERS". JOURNAL OF APPLIED POLYMER SCIENCE 100:791-802: 791. DOI:10.1002/APP.22680.
• HONG, SEUNGHUN; SUNG MYUNG (2007). "NANOTUBE ELECTRONICS: A FLEXIBLE APPROACH TO MOBILITY". NATURE NANOTECHNOLOGY 2: 207–208. DOI:10.1038/NNANO.2007.89
• MEO, S.B.; ANDREWS R. (2001). "CARBON NANOTUBES: SYNTHESIS, PROPERTIES, AND APPLICATIONS". CRIT. REV. SOLID STATE MATER. SCI. 26(3):145-249: 145. DOI:10.1080/20014091104189.
• KOLOSNJAJ J, SZWARC H, MOUSSA F (2007). "TOXICITY STUDIES OF CARBON NANOTUBES". ADV EXP MED BIOL. 620: 181–204. PMID 18217344
• EBBESEN, T. W.; AJAYAN, P. M. (1992). "LARGE-SCALE SYNTHESIS OF CARBON NANOTUBES". NATURE 358: 220–222. DOI:10.1038/358220A0