CNT synthesis and functionalization Pantea Fathi KTH, Forum 105 SE-164 40 KISTA, Stockholm, Sweden
Objective:
The aim of this report is introducing different methods
for synthesis ,purification and functionalization of CNT.
CNT synthesis and functionalization Pantea Fathi KTH, Forum 105 SE-164 40 KISTA, Stockholm, Sweden
Objective:
The aim of this report is introducing different methods
for synthesis ,purification and functionalization of CNT.
Per.Mat-CNTs module - Title Page
Application of CNT and their advantages
Carbon Nanotubes Synthesis
Arc discharge
Laser Ablation
CVD
3. Purification techniques
4.Functionalization
4.1. Methods
Endohedral Functionalization
Exohedral Functionalization
Chemical functionalizations
Amidation of CNTs 15
Fluorination of MWNT 16
4.2. f-CNT applications
Removal of Azo dyes by functionalized MWNT 17
5.Conclusion and discussion
Outlines
Carbon Nanotubes Given their unique properties, what can carbon nanotubes be used for?
Image from http://en.wikipedia.org/wiki/Image:Kohlenstoffnanoroehre_Animation.gif, GNU free documentation license by http://de.wikipedia.org/wiki/Benutzer:Schwarzm
Carbon Nanotubes (CNT) 1D, Iijima in 1991 .
Fantastic Mechanical properties
stiffness &strength due to Sp2 bond
Much stronger structure than diamond
May replace steel in the future
Construction purposes like using nanocomposites -bridges and dams
Light- Low mass
Aerospace industry to build aircrafts and satellites.
Thermal and Electrical conductivity
Electrical devices as interconnects transistors , CMOS industry, Nanaowires
Carbon Nanotubes applications
Few drawbacks:
Difficulty of mass production for industrial purposes.
Secondly is the solubility of CNTs in the water
Several ways to synthesize CNTs for industrial purposes overcome the solubility issue by functionalization
Different methods of CNT synthesis
purification and then functionalization.
. Drawbacks
Arc discharge
first and simplest method to synthesize Carbon Nanotubes.
Two pure graphite electrodes are connected to DC generator in atmosphere of helium.
An inert gas is added to the chamber which does not react with carbon.
Electric current is run thorough electrodes and therefore Carbon is deposited into cathode from anode and CNT are shaped in the middle .
quite perfect about few micro meters long
inner tube is 1-3 nm and outer tube in MWNT 10 nm in diameter.
Drawback
If both of the electrodes are made of graphite (mixture of CNTs along with fullerene, sheets of graphite, amorphous carbon)
more work to separate CNTs from its undesirable by-products.
4000 °C which is an extremely high temperature .
Electric arc method good for scientific study but not for industrial use .
Magnetic field in arc discharge synthesis
applying a magnetic field around the arc plasma for alignment purposes
a magnetic field have a high purity and fewer defects
electronic devices as nanowires for device fabrication .
Plasma rotating arc discharge
In this method the arc discharge technique is done by plasma rotating. As a result increased plasma volume more stable and homogenous plasma has been observed.
The rotation speed is 5000 rpm and temperature is found to be 1025°C which is high.
No catalyst is used in this method and after purification yield is increased to 90% .
laser is used to vaporize carbon from graphite ,a high temperature reactor at 1200 °C
inert gas is helium or argon
The process of laser ablation is like arc discharge method but in a lower temperature.
Continuous Laser
Pulsed Laser
difference is that pulsed laser requires much higher light density.
If we use pure graphite electrodes we can obtain MWNTs ,but to have uniform SWNTs, a mixture of graphite with Co, Ni, Fe or Y
The yield of this process is low and contains carbon Nanotubes along with Carbon Nanoparticles which is not ideal for industrial applications.
have a very high quality 10-15 in length.
Research to scale up the yield of this process.
Laser ablation
Chemical vapor deposition
The other common method is called Chemical vapor deposition (CVD)
several gases such as methane (CH4), carbon monoxide (CO) and acetylene (C2H2)
Heated substrate which is coated by catalyst like Ni, Al2O3, and SiO2
Inert gas such as nitrogen and hydrogen.
The energy source decomposes the molecule into active carbon atoms which then will be diffused on the substrate and CNTs begin to grow
The temperature 650–1000 oC which is quite high. The diameter of each nanoparticle defines the diameter of grow .
it is possible to have control over the diameter and length of grown CNT.
CVD process has mostly two main steps which first is preparing substrate by sputtering then to use thermal annealing to have catalyst nanoparticles on the substrate .
Large scale production and high yield production
Low cost
Continuous production instead of batch production
Control of the quality and CNT
Ability to manipulate
No separation of unwanted by-products
CVD process is extremely sensitive to the condition parameters .
Continues reactor and discontinuous reactor.
According to the original work done by Izaskun Bustero an optimal condition for CVD process for best yield
Results and discussion
Comparison of CNT different synthesis method:
CVD is the most promising method to make CNTs , industrial purposes.
Startup material is not graphite but some Carbon gas like methane .
A catalyst as tiny particles is also needed which will act like seeds to grow CNT diameter of the CNT can be chosen by the size of catalyst particles .
experiment can be run from minutes to hours in order to grow CNTs as long as required.
Almost lower temperature much higher yield and more control over the process quality lenth and diameter
Purification techniques Oxidation By oxidation we can partially purify CNTs from impurities ( time and temperature of exposure of the process are very important) . While oxidation –COOH or –OH groups are generated which help the attachment of organic or inorganic material to increase solubility. Best way is to mildly oxidize them with H2O2 and H2SO4 which only causes oxide defects. Acid treatment By acid treatment mostly metal catalysts are removed by the reaction with Nitric acid or Sulfuric acid or a mixture of both. Annealing In this method a very high temperature is applied (800-1800 °C) in a vacuum atmosphere which caused CNT atoms to rearrange and form a perfect CNT very high temperature ,metal is melted and also can be removed from the reaction Ultrasonication Ultrasonic created a low pressure and high pressure waves in the liquid and it improves the reaction and causes reactants to be mixed it forces particles to vibrate and disperse in the liquid evenly. Magnetic Purification Ultrasonic while ferromagnetic catalyst will be removed from SWNT. Suspension is mixed with Zirconium Dioxide (ZrO2) or Calcium Carbonate (CaCO3) and the bath is trapped among a magnet Micro filtration By this method while we have a mixture of materials along with carbon nanotubes by using a membrane. Purification step 1. Purification process sample was used in HCl, Acid Nitric HNO3, and Hydrofluoric Acid HF 2. Sonication (Ultra Sonication) in HF for 30 ...
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Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
B) covalent sidewall functionalization A) Covalent defect-group functionalization C) Noncovalent with surfactants D) Noncovalent exohedral polymers E) endohedral functionalization CNTs have high mechanical strength, thermally and electrically conductive, extremely light with low mass and high aspect ratio (surface to volume ratio). To use these phenomenal properties homogeneously dispersed in nanocomposites to preserve their characteristics. As CNTs have a hydrophobic structure and agglomerate because of vandervalse forces ,they do not disperse evenly in the liquid . Need to align CNTs and prevent them from agglomerating so that they can be even evenly distributed in nanofluids. . Functionalization of Carbon Nanotubes
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Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
- Chemical Functionalization Methods
Endohedral Functionalization
Endohedral Functionalization
Modification of CNT by putting nanoparticles inside the tube.
Change the hydrophobic structure to hydrophilic and make them as solvents.
Filling Nanotubes with nanoparticles to add the characteristics of the Nanoparticles inside the Carbon Nanotubes to fantastic phenomenal of CNT.
This method itself is sub categorized to two methods:
Putting CNT inside the suspension containing nanoparticles so that it can penetrate the tube internal site
and stay inside the CNT
Depends on surface energy(surface tension ) of the liquid.
Experiments show that if surface tension of the liquid is more than 200 mN/m, liquid can fill the Nanotubes
2. Are filled with a material which reacts with it and then produces nanoparticles which are trapped
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Pencil image thanks to http://www.flickr.com/photos/orangeacid/204163563/ (creative commons license)
Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
- Exohedral Functionalization
Exohedral Functionalization is modification of external part of CNTs like side walls .
This method itself is subcategorized into three main methods :
Covalent Exohedral functionalization-Defects
defect in CNT = best place for functionalization.
(Stone wall )
Covalent Exohedral functionalization -Functional groups
Side wall functionalization & to attach more functionalized group.
Noncovalent exohedral functionalization- Polymer wrapping
wrapping CNT in polymer, surfactants and peptides (smaller amino acids in length).
By wrapping the polymer around the CNT there is a phenomena called Pi stacking.
Pi stacking is when the P orbitals of CNT and functionalized group interact with each other and cause less stability.
In this type of functionalization electrical and optical properties of CNTs are not damaged and perturbed but because of poor interaction of p orbitals, stability is quite low .
As experiments show there is an improved electrical property of the polymer
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Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
- There are also several chemical functionalizations which we briefly mention in the following :
Amidation – Formation of Carbon Nanotube-Acyl Amides
Fluorination of Nanotubes
Chlorination of Carbon Nanotubes
Bromination of MWCNTs
Hydrogenation of Carbon Nanotubes.
Addition of Radicals
Addition of Nucleophilic Carbenes
Sidewall Functionalization through Electrophilic Addition
Addition of Nitrenes
Nucleophilic Cyclopropanation
Azomethine Ylides .
Diels-Alder Reaction
Sidewall Osmylation of Individual SWCNTs
Aryl Diazonium Chemistry –
Electrochemical Functionalization
Cathodic Coupling
Anodic Coupling Chemical functionalizations
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Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
Amidation of CNTs Amid is an organic compound as a functional group that has (R-C=O) attached to a nitrogen atom
This kind of functionalization can only be done of the CNTs which are already are carboxyl-functionalized (-COOH).
to treat it with Thionyl chloride (SOCl2) to substitute the (-OH)with chlorine and then add octadecylamine as shown in figure 18. octadecylamine Thionyl chloride to substitute the (-OH)
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Pencil image thanks to http://www.flickr.com/photos/orangeacid/204163563/ (creative commons license)
Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
- Fluorination of MWNT This process can be done on already functionalized CNTs by carboxyl group then they can be functionalized by fluorine .
further functionalization meaning that we can remove the fluorine and attach other functional groups.
This process can be continues by removing fluorine and replacing it with other functional group .
By this process there will be no damage imposed to CNT sidewalls and temperature is low about 150 °C to 500 °C. In this case for maximum fluorination can be achieved using iodine pentafluoride IF5, which leads to composition of C-F bonds . Experiments show electrical resistance of fluorinated SWCNTs has dramatically increased.
Further functionalization ,substituting fluorine can be done in the group of f-CNT.
Like adding functionalized groups .
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Pencil image thanks to http://www.flickr.com/photos/orangeacid/204163563/ (creative commons license)
Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
Applications Water filtration 2007 World Health Organization reported 1.1 billion people ,population 2050 = 9 billion People .
Limited water source ,water contamination ,toxic pollutants and hazardouse chemicals is a great danger for animals and human .
Dye =toxic polutant (textile, paper and carpet industries waste water )
cause environmental contamination they accumulate in nature and cause high toxicity
chronic effect on human health (concentration and time of exposure)
f-MWNT can remove dyes
High aspect ratio (surface to volume) it has high porosity and ability to adsorb substances .
f-MWNT are hydrophilic and they have the ability to form bonds with organic materials c=c.
Adsorption is considered superior technique for filtration purposes:
Low cost, availability, simplicity and ease of operation.
Even after oxidation with nitric acid CNTs showed exceptional enhanced adsorption.
Therefore f-MWNT have been successfully used in this application
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Pencil image thanks to http://www.flickr.com/photos/orangeacid/204163563/ (creative commons license)
Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
Coclusion In this presentation we briefly talked about different methods of CNT
Synthessis, Purification and Functionalization methods .
Among all physical synthesis metods
CVD was found to be the most promising(High Yield, Process Control ,Lower Temprature)
Some chemical functionalization were discussed required less temprature
and easier to handel
Purpose of Functionalization:
To add CNT properties to other materials
To make CNTs soluble in nanofluids
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Pencil image thanks to http://www.flickr.com/photos/orangeacid/204163563/ (creative commons license)
Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck
Coal image from wikipedia: This image is a work of the "Minerals in Your World" project, a cooperative effort between the United States Geological Survey and the Mineral Information Institute. The images were featured in the "Minerals and Materials Photo Gallery" on the website of the U.S House Subcommittee on Energy and Natural Resources. As a work of the U.S. federal government, the image is in the public domain.
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