Fellow bloggers, it’s good to finally be back posting again on Sungwoo’s Blog for all of you to enjoy! For the past few days, I’ve been researching deep into the subject of carbon nanotubes for my chemistry class, pulling information on just about everything the topic has to offer. Today, I’m sharing with you the wonder of this nanotube- ranging anywhere from what it is, to what its applications are in society.
First things first: what exactly are carbon nanotubes (CNTs)? Well, they are odourless tube-shaped materials composed of an array of carbon atoms, and they are so small in diameter that it’s measured in nanometres! This means that a single strand of CNT is 10,000 times smaller than a human hair. There are many different types of carbon nanotubes, such as single-walled (SWNT) and multi-walled (MWNT), but the main similarity is the graphite layer, which is the main material behind CNTs. Pure graphite is a natural form of carbon, and can be mined around the world. To make CNTs, huge numbers of graphite particles must be mined to synthesize nanotubes (Litherland, n.d.). The graphite is spread out in a hexagonal mesh of carbon chains, and rolled up in a tube as seen above. They are quickly increasing in popularity due to its strength, while staying light in weight; this makes CNTs an exceptional building material (CNT Technology Overview, 2017)
Despite just being composed of carbon atoms, creating a CNT is a lot more complicated than I expected. I learned that there were several methods in synthesis, but the most common ones were laser ablation and chemical vapor deposition (CVD). Laser ablation is exactly what it sounds like- using a higher-power laser, a solid block of pure graphite is heated inside a furnace to about 1200 degrees Celsius, vaporizing the graphite into particles. The residue is then collected by a cooled collector, eventually
gathering enough to form a mat of “ropes”, each rope representing a CNT. The great thing about laser ablation is that it can produce a decently large quantity of high-quality CNTs; however, the process is very expensive due to the pure graphite used, and other methods are capable of producing larger quantities of carbon nanotubes at a cheaper price (Nanowerk, n.d.).
Another method of producing CNTs is chemical vapor deposition, which is also used to
form various carbon-based materials, such as carbon fibre and filaments. In CVD, a hydrocarbon is decomposed through tubes drilled into silicon, where there are iron nanoparticles at the bottom of the tube. As the hydrocarbon makes contact with the particles, it initiates to create nanotubes through the drilled holes, giving it a long and aligned shape (NCBI, 2014). To expand these tubes, the carbon nanotubes that were created link up to form large quantities of polymers on the surface of the silicon, with the help of catalysts such as nickel, cobalt, and iron (Massachusetts Institute of Technology, 2015). CVD is currently the standard method of creating CNTs, as mass amounts can be created at a lower price than other techniques (NCBI, 2014). To learn more about chemical vapor deposition, watch this video here.
You might be wondering: what forces could possibly be holding such a thin material together that keeps it even stronger than steel? Well, each carbon nanotube is made up of repeating carbon atoms held together by a strong, interlocking covalent bond, a
type of intramolecular force occurring between non-metals. This bond holds hexagons of carbon atoms together into one big molecule, without any weak points in its lattice. This gives CNTs very high tensile strength, which is the force an object can withstand before tearing apart. Even steel has weak points around its structure; now I can clearly see how each nanotube has a tensile strength of 100 times greater than steel (Booker & Boysen, n.d.)!
The covalent bonds also play a role in the very high thermal conductivity of CNTs, which is one of the main properties that make them so useful in society. Unlike metals, which rely on the movement of electrons to conduct heat, the covalent bonds between carbons vibrate to conduct heat. This results in the carbon atoms themselves actually moving to create more thermal energy, making carbon nanotubes extremely good conductors (Booker & Boysen, n.d.).
As there are no charged ends at any areas around the molecule, I discovered that
CNTs are non-polar molecules. This means that there is only one intermolecular force present: London Dispersion. The constant electron clouds on the surface of the CNTs create a mild electrical attraction, which we can feel as “sticky”. Additionally, since the molecule is non-polar, it is insoluble in water, a polar molecule (AZoNano, 2017). In my opinion, all these properties seem to point out one fact: carbon nanotubes seem to carry many more advantages than traditional materials today!
So what exactly can these seemingly perfect nanotubes do? As of today, CNTs can be
applied to good use in several different fields, but the one that intrigued me most was in the medical field, where carbon nanotubes are used to really help people function properly. For example, studies have shown how lacing CNTs to the top of dental implants improve the overall quality, as the teeth adhere much better to carbon nanotubes than just the traditional titanium implants (UnderstandingNano, n.d.).
Just when I thought carbon nanotubes couldn’t get any cooler and useful… I came across something spectacular!
It appears that when CNTs are woven together with a form of yarn, and filled with wax, artificial muscles are the result! This can be life-changing for many people suffering from severe muscle damage, as it is fully functioning and can adjust itself to the body without issue. Not only this, it can lift up to 200 times more than the normal human muscle (UnderstandingNano, n.d.)! I think that’s the closest we could come to having superhuman strength… Watch a cool video demonstration on what carbon nanotube muscle looks like here.
Imagine having a laptop or TV… that can bend and fold without damage! Look no further, as the improvement of CNT technology might lead to flexible electronics in the
near future. At the University of Tokyo, researchers were able to create fully-functioning organic light-emitting diode (OLED) displays, bound with a rubbery nanotube-based conductor. Flexible, low-cost, and undoubtedly cool, these displays may find their way into all electronics in the future (Strickland, 2009)!
As if the improvement in the electronic industry wasn’t enough, carbon nanotubes have the potential to be used as cancer treatment. As studies have shown, when mice with kidney tumours had CNTs injected into the area of tumours, and had near-infrared lasers blasted at the tube, 80% of mice saw a complete disappearance of the tumours! I realized this was due to the covalent bonds within the CNTs; with heat being added on, each carbon atom ends up moving around to create even more heat, killing the surrounding cancer cells. However, it’s still not proven if it’s toxic for humans, so further development is necessary (Strickland, 2009). See the diagram below.
After all these advantages of having carbon nanotubes all around us, then why hasn’t it been developed fully yet? Well, there is one big problem with the CNTs: its production has a dangerous impact to the environment, and even humans.
Research suggests that when chemical vapor deposition is used for synthesis, several hundred tons of chemicals, including greenhouse gases and air pollutants, are released into the air every year (Bettex, 2010). Additionally, many of these particles may end up in aquatic wildlife, where it can build up to stop algae growth. Without algae, many ecosystems won’t survive as it is used as a food source and as a filter to keep water clean (Heimbuch, 2011). However, according to the ACS Nano website, by reducing certain steps in synthesis of CNTs, the emissions of harmful byproducts could reduce by up to 100 times.
Unfortunately, it might get worse from there. As I was researching for social impacts that CNTs might have, I found out how the leftover particles that float in the air can
make their way deep into our lungs. This can cause severe sickness and even mesothelioma, a cancer that “previously has been associated with only asbestos” (Lulea University of Technology, 2011). Thankfully, it is highly unlikely that tiny particles of CNT could cause such damage, but if the buildup reaches high numbers in the lung, consequences will certainly arise.
Thankfully, there are some positive impacts of using carbon nanotubes. Using high-strength CNTs in terrestrial and air transport vehicles could result in a 25% decrease in overall weight, and reduce oil consumption by nearly 6 million barrels per day within the next 10 years. Worldwide, the use of petroleum and other fuels will also drop by 25%. This boosts the economy greatly in Canada specifically, as the government can save billions of dollars a year due to less oil imports from foreign countries. Furthermore, carbon nanotubes may even find its way into power distribution lines, which is predicted to reduce transmission losses by 41 billion kilowatt hours annually! This leads to huge savings in coal and gas usage, allowing the economy to thrive financially. No wonder the demand has raised from 46,000 metric tons/year to 153,000 metric tons/year (National Nanotechnology Initiative, 2014); with all these economic benefits, CNTs are materials that are definitely worth the development.
In conclusion, I believe that the application of carbon nanotubes can be beneficial to everybody. Despite the scares of health issues, and negative environmental impacts, there’s nothing that can’t be fixed or improved! Within the near future, I hope to see this form of nanotechnology fully developed and waiting to be used in the everyday lives of all people. I mean, with those CNT muscles, I could be 200 times stronger!
What are your thoughts on CNTs? Do you believe carbon nanotubes are worth all the attention it’s been getting? Let me know down in the comments!
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