UNIVERSITY OF ENGINEERING AND MANAGEMENT,JAIPUR,RAJASTHAN

TOPIC: NANO TUBES

BRANCH ECE

* SOUDIP SINHA ROY .

.

LIST OF DISCUSSION

CARBON NANOTUBE BORON

NANOTUBE

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

PROPERTIES• STRENGTH

• ELECTRICAL

• THERMAL

• DEFECTS

• ONE-DIMENSIONAL TRANSPORT

• TOXICITY

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.

NANOTUBES’ EXCELLENT STRENGTH TO WEIGHT RATIO

CREATES THE POTENTIAL

TO BUILD AN ELEVATOR TO

SPACE.

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.

BORON NANOTUBE

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.

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REFERENCES• HTTP://WWW.NEWS-MEDICAL.NET/NEWS/22799.ASPX

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