ABSTRACT- .least .one .dimension .less .than .100

ABSTRACT- .The .nanotechnology .is .a system .of .innovative .methods .to .control .and .manipulate .matter .at .near .atomic .scale .to .produce .new .materials, .structures, .and .devices. This .paper .gives .a .review .on .the .growth, .structural .properties .and .practical .applications
.of .carbon .nanofibers .as .compared .with .those .of .conventional .carbon .fibers. Carbon .nanofibers .could .be .produced .via .the .catalytic .chemical .vapour .deposition (CVD) .as .well .as .the .combination .of .electro .spinning of .organic .polymer .and .thermaltreatment. Nanotechnology .offers .the .potential .for .tremendous .improvement .and .advances .in .the .development .of .commercial .products .that .may .benefit .society, .such .as .integrated .sensors, .semiconductors, .medical .imaging, .drug .delivery .systems, .structural .materials, .sunscreens, .cosmetics, .and .coatings. Nanotechnology .is .one .of .the .most .enabling .technologies .across .the .world. By .2020, .the .global .market .for .nanotechnology-related .products .is .predicted .to .reach $3 .trillion .and .employ .2 .million .workers .in .the .United .States .alone 1.

Keywords-Nano .sensor, .Polymeric .composites, .carbon .fiber,
.Nanotube, .Graphene, .Nanotechnology, .Nanomaterial’s, .chemical .sensors, .Radio .frequency .identification .sensor.

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INTRODUCTION:

The .Nano-objects .are .nanomaterial’s .that .have .at .least .one .dimension .less .than .100 .nanometre. .Nanoparticles .are .a .specific .class .or .subset .of .these .Nano-objects, .having .three .dimensions .that .are .less .than .100 .nanometres3, .7, .9, .10. .The .Nanoparticles .exhibit .unique .properties .because .of .their .Nano .scale .dimensions. .In .recent
.years, .nanotechnology .has .emerged .out .as .the .backbone .of .contemporary .devices .based .on .the .sensors. .It .has .opened .up .new .dimension .for .the .Nano .devices .in .numerous .fields. .Since .this .technique .is .unique, .better .and .efficient .than .previous .ones .in .many .aspects .like .the .exceptional .characteristics .of .Nano .composites .and .materials .15, .16, .31.Carbon .nanofibers .are .linear, .no .continuousfilaments .that .are .different .from .continuous, .several .micrometre .diameter .carbon .fibres. .The .commercially .available .carbon .nanofibers .around .the .world .is .calculated .as .500 .t/y. .Carbon .nanofibers .exhibit .high .specific .area, .flexibility, .and .super .strength .due .to .their .Nano .sized .diameter .that .allow .them .to .be .used .in .the .electrode .materials .of .energy .storage .devices, .hybrid-type .filler .in .carbon .fiber .reinforced .plastics .and .bone .tissue .scaffold .8. .It .is .envisaged .that .carbon .nanofibers .will .be .key .materials .of .green .science .and .technology .through .close .collaborations .with .carbon .fibres .and .carbon .nanotubes .11, .14,
.15. .

The .design .of .maintenance-free .and .passive .wireless .sensors .like, .gas .sensor .or .fire .sensor .is .already .being .thoroughly .tested. .The .other .emerging .fields .are .radio .frequency .identification .(RFID) .sensors .or .biological .sensors. .It .is .observed .that .various .properties .like .chemical, .mechanical .and .electrical .are .already .being .studied .and .many .such .fields .are .already .being .explored. .This .level .of .expertise .is .achieved .till .today .from .the .first .intervention .of .carbon .nanotubes .by .the .scientist .S. .Iijima .in .the .decade .of .1990’s. .The .investigations .have .predicted .a .very .important .factor .about .CNTs .that .their .activation .power .is .much .smaller .than .other .conventional .devices .and .it .comes .out .about .10000 .times .smaller .than .actual .requirements .of .micro .electro-mechanical .systems .(MEMS) .conventionally .used. .The .CNTs .are .that’s .why .truly .considered .as .sensing .elements .of .next .generation .151. .The .CNT .(Carbon .Nanotube) .has .been .discovered .by .Sumio .Iijima .in .1991 .184 .and .since .then .various . .devices .such .as .atomic .force .microscopy .probe .tip .168, .Nano .actuator .169, .nanotweezer .17, . .Nano .oscillator .18 .and .many .more .have .been .made .based .on .this .structure. .These .accomplishments .are .obtained .due .to .the .unique .characteristics .of .the .CNT .such .as .big .Young’s .modulus, .high .stiffness, .small .size, .light .weight, .high .aspect .ratio .12, .13 .and .interesting .electrical .properties .16, .20.

Let’s .consider .the .case .of .a .CNT .based .prototype .RFID .sensor. .It .is .observed .that .this .type .of .sensor .exhibit .unique .features .based .on .that .it .is .roughly .categorised .as .maintenance .free .sensor. .In .this .setup, .this .objective .is .obtained .if .the .sensor .antenna .measurements .are .used .in .a .controlled .way .and .the .simulation .are .obtained. .Such .a .CNT .Bucky .paper .can .be .easily .characterized .by .taking .into .consideration .the .sensitivity .and .dielectric .behaviour .of .the .sensor. .Another .emerging .application .of .CNT .can .be .its .ability .to .sense .the .harmful .gases .like .NH3 .19, .21, .and .22. .The .CNT’s .ability .as .sensors .to .measure .sensitivity .towards .NH3 .is .experimentally .verified .and .its .applicability .is .already .tabulated .in .different .studies. .In .the .feasibility .study .of .a .CNT .based .combinational .materials, .its .depositions .along .with .the .inkjet .printing .is .already .being .realised. .This .approach .is .helpful .in .achieving .the .various .typical .applications .of .CNT .based .sensors. .This .innovative .approach .is .again .one .of .the .emerging .application .domains .of .CNT’s .in .the .various .field .of .internet .communication .technologies .and .integrated .electronics .environments .27, .28, .36. .This .is .observed .that .there .is .a .demand .of .the .moment .of .a .sophisticated .architecture .which .may .be .so .innovative .that .it .can .be .easily .be .adopted .in .various .research .and .development .areas.There .are .many .interesting .applications .of .the .CNT .like .one .in .a .resonator .based .sensors. .These .sensors .can .be .used .in .many .sensing . .applications .such .as .gas .level .sensing, .metal .deposition .monitors, .chemical .reactor .monitors, .mass .detectors .and .biomedical .sensors .32, .33. .All .these .applications .follow .general .frequency .phenomenon .that .is .changes .in .mass .causes .a .shift .in .natural .frequency .and .the .resulted .frequency .shift .can .be .used .to .detect .or .predict .either .presence .or .concentration .of .the .attached .mass23, .24. .The .other .properties .of .CNTs .like .extremely .high .stiffness .and .light .weight .make .CNT .as .an .excellent .platform .to .make .a .high .frequency .resonance .based .sensor. .This .is .predicted .that .the .natural .frequency .of .10 .GHz-1.5 .THz .can .be .achieved .by .a .CNT .based .cantilever .or .bridge .beam .29. .This .value .is .among .the .greatest .value .reported .in .the .present .Nano-mechanical .resonators. . .In .the .case .of .resonator .based .sensors, .the .higher .frequencies .provide .more .sensitive .sensors. .The .research .has .shown .that .Nano .tubes .are .considered .to .be .a .continuum .models, .such .as .shell .or .beam, .with .no .vacancy .defect .30, .34, .and .35. .The .studies .are .going .on .the .resonator .frequency, .based .on .quantity .and .the .place .of .the .vacancy .defects .183. .The .method .and .devices .(SuFETs) .for .design .of .the .bioelectronics .sensors .has .been .proposed. .The .circuits .consist .of .the .superconducting .material .which .is .organic .generally .and .is .used .for .fabricating .solid-state .field-effect .transistor .(SuFET). .This .is .further .connected .to .a .nerve .fiber .by .a .simple .nanotube .contact. .There .may .be .a .traditional .low-ohmic .contact .also. .There .are .many .application .areas .of .organic .and .chemical .gas .sensors .which .are .very .promising. .These .include .the .design .and .fabrication .of .devices .built .using .carbon .nanotubes .(CNT)-based .FETs. .The .above .approach .of .designing .is .best .as .an .application .of .SuFETT. .Already .observations .has .revealed .that .the .range .of .picked .up .signals .varies .from .0.6 .nA .to .10 .A .with .frequencies .from .20 .to .2000 .Hz.

1. .Similarity .and .Difference .between .Carbon .Fibers .and .Carbon .Nanofibers:

Since .carbon .nanofibers .could .be .considered .as .the .1-D .form .of .carbon, .their .structure .and .properties .are .closely .related .to .those .of .other .forms .of .carbon, .especially .to .crystalline .three-dimensional .graphite, .turbostratic .carbons .and .to .their .constituent .2-D .layers. .Therefore, .several .forms .of .conventional .carbon .materials .should .be .mentioned .in .terms .of .their .similarities .and .differences .relative .to .a .carbon .nanofiber. .Especially, .a .direct .comparison .should .be .made .between .fibrous .carbon .materials, .because .the .carbon .fiber .acts .as .a .bridge .between .carbon .nanofibers .and .conventional .bulky .carbon .materials .27, .28. .In .this .section, .the .structures .of .carbon .fibers .as .well .as .VGCFs .are .described .with .a .strong .emphasis .on .the .similarities .and .differences .of .these .1-D .carbon .materials .39.

 

2. .Basic .Theory .and .Concepts .regarding .Nanomaterial’s:

Carbon
.fibers .represent .an .important .class .of .graphite .related .materials .that .are .closely .related .to .carbon .nanofibers, .with .regard .to .structure .and .properties. .Carbon .fibers .have .been .studied .scientifically .since .the .late .1950s .and .fabricated .industrially .since .1963. .They .are .now .becoming .a .technologically .and .commercially .important .material .in .the .aerospace, .construction, .sports, .electronic .device .and .automobile .industries. .

 

Fig. .1: .The .mechanical .properties .of .various .kinds .of .carbon .and .graphite .fibers .40.

 

The .global .carbon .fiber .market .has .now .grown .to .about .12 .500 .t/y .of .product, .after .40 .years .of .continuous .R .work .2. .Carbon .fibers .are .defined .as .a .filamentary .form .of .carbon .with .an .aspect .ratio .(length/diameter) .greater .than .100. .Probably, .the .earliest .documented .carbon .fibers .are .the .bamboo .char .filaments .made .by .Edison .for .use .in .the .firstincandescent .light .bulb .in .1880. .With .time, .carbon .fibers .were .replaced .by .the .more .robust .tungsten .filaments .in .light .bulb .applications, .and .consequently .carbon .fiber .R .vanished .at .that .early .time. .But .in .the .late .1950s, .carbon .fibers .once .again .became .important .because .of .the .aggressive .demand .from .aerospace .technology .for .the .fabrication .of .lightweight, .strong .composite .materials, .in .which .carbon .fibers .are .used .as .a .reinforcement .agent .in .conjunction .with .plastics, .metals, .ceramics, .and .bulk .carbons. .

The .specific .strength .(strength/weight) .and .specific .modulus .(stiffness/weight) .of .carbon .fiber-reinforced .composites .demonstrate .their .importance .as .engineering .materials, .due .to .the .high .performance .of .their .carbon .fiber .constituents. .Since .the .temperature .and .pressure .necessary .to .prepare .a .carbon .fiber .from .the .liquid .phase .is .at .the .triple .point .(T .= .4100 .K, .p .= .123 .kbar), .it .would .be .almost .impossible .to .prepare .carbon .fibers .from .the .melt .under .industrial .processing .conditions. .Carbon .fibers .are .therefore .prepared .from .organic .precursors. .This .preparation .is .generally .done .in .three .steps, .including .stabilization .of .a .precursor .fiber .in .air .(at .? .300 .?C), .carbonization .at .? .1100 .?C, .and .subsequent .graphitization .(> .2500 .?C). .Fibers .undergoing .only .the .first .two .steps .are .commonly .called .carbon .fibers, .while .fibers .undergoing .all .three .steps .are .called .graphite .fibers. .Carbon .fibers .are .generally .used .for .their .high .strength, .while .graphite .fibers .are .used .for .their .high .modulus .41, .42.