NANOSCIENCE AND NANOMATERIAL

          NANOSCIENCE AND NANOMATERIAL

 NANOSCIENCE 

NANOSCIENCE IS THE STUDY OF THE FUNDAMENTAL PRINCIPLES OF STRUCTURES WITH DIMENSIONS OF THE ORDER OF 1 TO 100 NANOMETERS (nm). THE STRUCTURE WITH SIZE RANGING BETWEEN 1 nm TO 100 nm ARE KNOWN AS NANOSTRUCTURE.

NANOTECHNOLOGY

THE BRANCH OF KNOWLEDGE DEALING WITH THE APPLICATIONS OF NANOSTRUCTURES AND NANODEVICES IS KNOWN AS NANOTECHNOLOGY.

GENERALLY, NANOTECHNOLOGY DEALS WITH STRUCTURES OF THE 100 NANOMETER OR SMALLER, AND IT INVOLVES DEVELOPING MATERIALS OR DEVICES WITHIN THE RANGE.

WHERE THESE TERMS ORIGINATED    

THE CONCEPT OF NANOTECHNOLOGY WAS FIRST USED BY RICHARD FEYNMAN IN A TALK TITLED "THERE IS PLENTY OF ROOM AT THE BOTTOM "GIVEN BY HIM AT AN AMERICAN PHYSICAL SOCIETY MEETING AT CALTECH ON DEC 29, 1959. IN THIS TALK, FEYNMAN DESCRIBED A PROCESS BY WHICH THE ABILITY TO MANIPULATE DESCRIBED A PROCESS BY WHICH THE ABILITY TO MANIPULATE INDIVIDUAL ATOMS OR MOLECULES MIGHT BE DEVELOPED.

NANOMATERIALS

THE MATERIAL REDUCED TO NANOSCALE ARE KNOWN AS NANOMATERIALS. THE NANOMATERIALS FALL INTO FOLLOWING CATEGORIES.

(A) INORGANIC NANOMATERIALS

(B) ORGANIC NANOMATERIALS

BASIC PRINCIPLES OF NANOSCIENCE AND NANOTECHNOLOGY

WE DEFINE NANOSCIENCE AS THE STUDY OD PHENOMENA AND MANIPULATION OF MATERIALS TO ATOMIC, MOLECULAR AND MACROMOLECULAR SCALES, WHERE PROPERTIES DIFFER SIGNIFICANTLY FROM THOSE AT A LARGER SCALE AND NANO TECHNOLOGIES AS THE DESIGN, CHARACTERIZATION, PRODUCTION, AND APPLICATION OF STRUCTURES, DEVICES, AND SYSTEMS BY CONTROLLING SHAPE AND SIZE AT THE NANOMETER SCALE.     

THERE ARE TWO APPROACH USED IN NANOTECHNOLOGY FOR THE FORMATION OF THE NANOMATERIAL:-

(1) BOTTOM-UP APPROACH 

(2) TOP-DOWN APPROACH

PHYSICAL AND CHEMICAL PROPERTIES OF NANOMATERIALS

#PHYSICAL PROPERTIES OF NANOMATERIALS

1. WHEN A BULK METAL IS REDUCED IN SIZE, THE CONTINUOUS LEVELS IN THE CONDUCTION BAND ARE REPLACED BY A SET OF DISCRETE ENERGY LEVELS AND A GAP OPEN UP.

2.THE COLOUR OF A CLUSTER DEPENDS ON ITS SIZE.

3.THE BAND GAP INCREASES AS THE PARTICLE SIZE DECREASE.

4. CARBON NANOTUBES ARE RESILIENT AND THEY HAVE HIGH TENSILE STRENGTH.

5. CARBON NANOTUBES HAVE HIGH THERMAL CONDUCTIVITY, DISPLAY MAGNETO-RESISTIVE EFFECT AT LOW TEMPERATURE.

#CHEMICAL PROPERTIES OF NANOMATERIALS

1. THE ABILITY OF NANOCLUSTERS TO REACT WITH OTHER SPECIES DEPEND ON CLUSTER SIZE.

2. NANOTUBES SERVE AS CATALYST FOR SOME CHEMICAL REACTIONS.

3. NANOTUBES CAN BE USED AS CHEMICAL SENSOR.   

APPLICATIONS OF NANOMATERIAL

1. CARBON NANOTUBES CAN BE USED IN MAKING FLAT PANEL DISPLAYS AND VACUUM TUBE LAMPS BY EXPLOITING THE FIELD EMISSION PROPERTY OF CARBON NANOTUBES.

2. CARBON NANOTUBES CAN BE USED IN FABRICATING HIGH-SPEED SWITCHING COMPONENTS FOR COMPUTERS

3. CARBON NANOTUBE HAVE APPLICATIONS IN BATTERY TECHNOLOGY.

4. CARBON NANOTUBE CAN BE USED AS SENSITIVE DETECTORS FOR VARIOUS GASES.

5. CARBON NANOTUBES CAN BE USED AS CATALYST FOR CHEMICAL REACTIONS

6. CARBON NANOTUBES CAN BE USED AS HEAT SINKS FOR CHIPS USED IN ADVANCED COMPUTING.

7. NANOSPHERES OF INORGANIC MATERIALS CAN BE USED AS LUBRICANT AS THEY ACT AS NANO SIZED BALL BEARINGS.

8. NANOMATERIALS MAY BE USED FOR MAKING STATE OF ART BATTLE SUITS WHICH CAN WITHSTAND BLAST WAVES.

9. PERFORMANCE AND PROPERTIES PROPERTIES OF PAINTS ARE IMPROVED WHEN NANOPARTICLES ARE INCORPORATED IN THEM.

10. MEDICAL IMPLANTS

CURRENT MEDICAL IMPLANTS SUCH AS ORTHOPEDIC IMPLANTS AND HEART VALVES ARE MADE OF TITANIUM AND STAINLESS STEEL ALLOYS BECAUSE THEY ARE BIOCOMPATIBLE.         

CARBON NANOTUBE

CARBON NANOTUBES ARE CYLINDRICAL FULLERENCES. THESE TUBES OF CARBON ARE USUALLY ONLY A FEW NANOMETERS WIDE, BUT THEY CAN RANGE FROM LESS THAN A MICROMETER TO SEVERAL MILLIMETERS IN LENGTH. THEY OFTEN HAVE CLOSED ENDS BUT CAN BE OPEN-ENDED AS WELL. THERE ARE ALSO CASES IN WHICH IT REDUCES IN DIAMETER BEFORE CLOSING OFF...

TYPES OF NANOTUBE

(A) SINGLE WALLED TUBE:-

 THESE TUBES HAVE A SINGLE WALL ONLY. MOST SINGLE WALLED NANOTUBES HAVE A DIAMETER CLOSE TO 1 NANOMETER WILL A TUBE LENGTH THAT CAN BE MANY MILLION TIMES LONGER THAN THE DIAMETER. THE STRUCTURE OF A SINGLE WALLED TUBE CAN BE CONCEPTUALIZED BY WRAPPING A ONE ATOM THICK LAYER OF GRAPHITE INTO A SEAMLESS CYLINDER.

(B) MULTI WALLED NANOTUBE:-

 MULTI WALLED NANOTUBE CONSIST OF A MULTIPLE LAYERS (COAXIAL TUBES) OF GRAPHITE. THE INTERLAYER DISTANCE IN MULTI WALLED NANOTUBE IS APPROXIMATELY 330 A DEGREE. THE MORPHOLOGY AND PROPERTIES OF DOUBLE WALLED NANOTUBE ARE SIMILAR TO THOSE OF SINGLE WALLED NANOTUBE BUT THEIR RESISTANCE TO CHEMICALS IS SIGNIFICANTLY IMPROVED.

(C) NANOTORUS:-

NANOTORUS IS A THEORETICALLY DESCRIBED CARBON NANOTUBE. NANOTORI ARE PREDICTED TO HAVE MANY UNIQUE PROPERTIES SUCH AS VERY LARGE MAGNETIC MOMENTS.

FABRICATION OF CARBON NANOTUBES

(1)  CARBON ARC METHOD

A POTENTIAL OF 20-25V IS APPLIED ACROSS CARBON ELECTRODES OF 5-20um DIAMETER AND SEPERATED BY 1mm AT 500torr PRESSURE OF FLOWING HELIUM. CARBON ATOMS ARE EJECTED FROM THE POSITIVE ELECTRODE AND THEY FORM NANOTUBES AT THE NEGATIVE ELECTRODE. AS THE TUBES FORM, THE LENGTH OF THE POSITIVE ELECTRODE DECREASES, AND A CARBON DEPOSIT FORMS ON THE NEGATIVE ELECTRODE. TO PRODUCE SINGLE WALLED NANOTUBES, A SMALL AMOUNT OF COBALT, NICKEL, OR IRON IS INCORPORATED AS CATALYST IN THE CENTRAL REGION OF THE POSITIVE ELECTRODE. IF NO CATALYST IS USED, THE TUBES ARE MULTI-WALLED, TYPES, WHICH ARE NANOTUBES WITHIN NANOTUBES.

(2) CHEMICAL VAPOR DEPOSITION METHOD

IN THIS METHOD HYDROCARBON GAS SUCH AS METHANE IS DECOMPOSED AT 1100 DEGREE CELCIUS. AS THE GAS DECOMPOSES, CARBON ATOMS ARE PRODUCED. THESE ATOMS, USED TO CONDENSE ON A COOLER SUBSTRATE CONTAINING CATALYST SUCH AS IRON TO FORM NANOTUBES.

   APPLICATIONS OF CARBON NANOTUBES

1. FIELD EMISSION AND SHIELDING

WHEN A SMALL ELECTRIC FIELD IS AN APPLIED PARALLEL TO THE AXIS OF THE TUBE, ELECTRONS ARE EMITTED AT A VERY HIGH RATE FROM THE ENDS OF THE TUBE. THIS IS CALLED FIELD EMISSION.

2. COMPUTER

THE FIELD EFFECT TRANSISTORS ARE SWITCHING OF COMPUTERS.

3. FUEL CELLS

CARBON NANOTUBES HAVE APPLICATION IN BATTERY TECHNOLOGY, LITHIUM, WHICH IS A CHARGE CARRIER IN SOME BATTERIES, CAN BE STORED INSIDE NANOTUBES.

4. CHEMICAL SENSOR

5. CATALYSIS

A CATALYTIC AGENT IS A MATERIAL, TYPICALLY A METAL OR ALLOY THAT ENHANCES THE RATE OF CHEMICAL REACTION.