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Carbon nanotubes and applications

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Miguel Cayón Ruisánchez

on 28 May 2013

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Transcript of Carbon nanotubes and applications

Carbon Nanotubes
and applications Applications Multumesc
pentru atentie It is divided into two major groups - A sensor is a device which detects certain characteristic of the external environment

- Also tansform it so it can be transmitted and mesurable Tubes made by carbon atoms
Diameter can be smaller than 1nm
Lenth up to 1 mm
Great Mechanical, Electric and Thermal Properties

There are two different types:
- Single-Walled NanoTubes (SWNT)
- Multi-Walled NanoTubes (MWNT) Electrical properties What are
carbon nanotubes? - Wide range of conductivities
From semiconductors to superconductors
- Currents of a thousand millions of A/cm2
1000 times more than cupper wires
- Properties do not depend on the lenth of the tube - They are the most interesting applications of CNT

- Miniaturization of devices

- They can work as silicon but at the molecular level, where the semiconductor stop working.

-The most interesting devices where CNT can be very useful are: Storage Chemical and biological sensors Substrate Method SWNT Miguel Cayón Ruisánchez

Gheorghe Asachi Techinical University
Faculty of Electrical Engineering
Cord.: Prof.dr.ing. Cristian Fosalau MWNT Carbon nanotubes
properties Mechanical properties - They are the most resistant fiber that can
be manufactured nowadays
- Tensile strenght up to 150 gigapascals
- Young's modulus around 1 terapascal
- Specific strenght of 48,000 kN·m·kg-1
compared to high-carbon steel's 154 kN·m·kg-1
- Pressure up to 55 GPa without deformation Thermal properties - They are very good thermal conductors
- Thermal conductivity about 3500 W·m-1·K-1
Very good compared with copper which is 385 W·m-1·K-1
- The temperature stability is estimated to be up to 2800 °C in vacuum and about 750 °C in air Carbon
discovery Chapter I. What are Carbon Nanotubes?




4.http://www.euroresidentes.com/futuro/nanotecnologia/diccionario/nanotubos.htm Chapter II. Properties of carbon nanotubes


6.Kumar S., Dang T.D., Arnold F.E., Bhattacharyya, A.R. Min B.G., Zhang X., Vaia, R.A., Park,C., Adams W.W., Hauge A., Smalley A., Ramesh S., Willis P.A. (2002) “Synthesis, Structure, and Properties of PBO/SWNT Composites” Macromolecules 35: 9039-9043.

Chapter III. Discovery of carbon nanotubes


8.http://www.interempresas.net/MetalMecanica/Articulos/105592-Nanotubos-de-carbono-el-material-de-la-nueva-era.html Chapter IV. How to produce carbon nanotubes?




12.Gojny F.H., Nastalczyk J.,Roslaniec Z., Schulte K., (2003) “Surface modified multi walled carbon nanotubes in CNT/epoxy-composites” Chemical Physics Letters 370:820–824.

13.Seeger T.,G. de la Fuente2,Maser W.K ,Benito A. M.,Callejas M.A, Martinez M.T (2003) “Evolution of multiwalled carbon-nanotube/SiO2 composites via laser treatment” Nanotechnology 14: 184–187.

Chapter V. Applications of Carbon Nanotubes





18.White A, Best S, Kinloch I. (2007) “Hydroxyapatite-carbon nanotube composite for medical applications: A Review” Int. J. Appl. Ceram. Technol. 4(1):1-13.

19.Baughman R (2002) “Carbon Nanotubes—the Route Toward Applications” Science 297: 787-792. References How to produce
carbon nanotubes? Essentially two-steps process:

- Catalysts are prepared

- Nanotubes grow

Temperatures between 650 and 900 °C Dispersing nanoparticles of a
transition metal on a substrate Two gases are mixed in the reactor, a process gas and a carbon source gas Laser ablation Consists in vaporize a graphite target radiating it with a laser pulse

Yield of 70% by weight

Diameter can be controlled varying the temperature

Only SWNT can be obtained Electric arc discharge Electric arc between two facing electrodes

Temperature of about 3.000 ° C

The typical yield is around 30% by weight

We can obtain SWNT and MWNT In electronics In sensors In materials In Energy FIELD EMISSION:

-Field emission is a form of taking away electrons from a solid by applying a electric field

-Carbon nanotubes are excellent field emitters

This have practice application in:

Flat screens: Lower consumption, high brightness, wide viewing angle, and fast response

Cathode ray tubes: Carbon nanotubes as field emitters can be the source of electrons in cathode ray tubes

X-Ray source: Carbon nanotubes can replace thermionic emitters used in conventional X-ray sources

Microwave amplifiers

Scanning electron microscopes

Gas discharge tubes in telecommunication networks

Luminescent tubes and lamps NANOCIRCUITS:

- Nanowires:

CNT conduct heat as well as diamond

Structural strength allow the transport huge amounts of current without damage; even currents that could destroy the copper or gold

In a perfect nanotube electrons travel without any resistance and without any dispersion -Diodes:

Combining metallic and semiconducting nanotubes a diode is obtained

The p-n junction is achieved by polarizing one half of a nanotube with a positive voltage and the other half with a negative

- Transistors: MEMORIES:
Memories made with CNT are an alternative for actual RAM memories
The advantages are: They are nonvolatile, faster, cheaper, radiation resistant, with an almost unlimited life, high capacity data storage and less current consumption

Can be constructed using very small arrays of metal carbon nanotubes arranged similar to the bristles of a brush

This devices convert light into electricity and viceversa
CNT when illuminated with visible light generated electrical currents Detect the presence of certain substances

- CNT have the property to change their resilience and capacity to react chemically with the substance to be detected

- Nanotubes with defects to detect molecules that occupy the voids

- CNT can also detect the presence of substances with charge

Advantages: Fast, great sensibilty and small size Mechanical sensors Used to detect and measure forces

When CNT is submitted to a force, small displacements occur in atomic structure and electrical properties are altered Electromagnetic sensors They detect the presence of electromagnetic waves

There are four reasons why CNT can be used for this kind of sensors:
1. They produce electrical currents when they are illuminated
2. The photoluminescence of the SWCNT
3. They absorb visible and infrared radiation
4. Microwaves induces field emission in them Thermal sensors Used to measure the temperature or the changes occurring in it

CNT resistance changes with temperature
Resistance increases substantially linearly with the temperature
Wavelengths of the infrared spectrum present pyroelectricity in CNT There are two ways of forming matirials with CNT:

Grouped to form packs Mixing with other materials to form compounds Fiber with nanoscale diameter and length much bigger than the radius

Individual CNT are preferred for molecular electronic applications
Packs are better for structural applications
CNT held together by Van der Waals forces Materials with zero dimensions: three dimensions are nanoscopic. Nanoparticles

One dimension Materials: two dimensions are nanoscopic

Two-dimensional materials: one dimension is nanoscopic

Materials with their three macroscopic dimensions Can be spun to create cords and wires Used to create films and coatings Conversion

- Physisorption method: Storage involving only the van der Waals forces

- CNT have closed curvature and its hollow interior

- Large specific area per volume unit

Device formed by two armors separated by a dielectric
Armor are made with a very high porosity material
- High yield
-High specific energy (4 kWh / kg)
-Very high specific power (5 kW / kg)
-Short charging time

Hydrogen enters through the anode dissociate into protons and electrons
Oxygen enters by the cathode
Anode and cathode are separated by a membrane which only permits the passage of protons
Electrons are forced to flow through the electrical circuit
The electrocatalyst should be a porous, high surface area, inert and good conductor

Transit of lithium ions between the cathode (typically LiCO2) and the carbon anode
The use of CNT improve the anode because their high surface area

CNT may be the semiconductor material that generates current when excited by light rays

Improve the movement of photogenerated charges to the electrode surface using its high conductivity Hydrogen and other gases Supercapacitors Hydrogen cells Lithium Ion Batteries Solar cells Japan, 1991 The first record described above carbonaceous filament production 1889 1958 Development of electron microscopy, then occurs the production of filaments between 100 and 200 nm Filaments range with diameter between 10 and 100 nm 1953 Start studies about the generation of carbon filaments by catalytic processes 1970s Discovery of fullerenes 1985 Discovery of the nanotubes 1991
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