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  • 100 times stronger than steel are fascinating materials that could *channel* a kaleidoscope

  • of futuristic technologies. Theyre often hailed as a key *conduit* for a speedy transition

  • to a zero-carbon energy future. However, while these graphene-based tiny tubes have been

  • overhyped as revolutionary for about 30 years, they haven't made it to the market yet. But

  • we're seeing slow progress towards interesting use cases, like a recent advancement that

  • could turn CNTs into *hot stuff* for generating clean electricity out of waste heat. Let's

  • revisit carbon nanotubes and see how things are shaping up.

  • I'm Matt Ferrell ... welcome to Undecided.

  • About a year ago I covered how carbon nanotubes might be able to boost solar energy in another

  • video, so I thought it was a good time to revisit the topic. And I'm not a scientist,

  • but like to look at these technologies from a broader view, how they may impact our lives,

  • and if they're actually coming to market. I know you've probably heard a lot of promises

  • on graphene and carbon nanotubes that haven't been delivered yet, but researchers are unleashing

  • new avenues to *channel* their phenomenal potential, as well as finding ways to improve

  • their manufacturing. And it's that last point that's one of the biggest sticking points

  • with CNTs.

  • Let's refresh your memory *and mine as well* on what’s meant to be the *hollow grail*

  • of the nanotechnology field. Although CNTs were first observed

  • in the late 1950s , formed by two layers of graphene. Not exactly catchy names, but very

  • accurate.

  • Since Iijima brought them to life, CNTs have been associated with endless fanciful applications.

  • Like a space elevator to name the most *out there* prediction. However, the *astronomical*

  • promise has never been fulfilled. One reason for this is that when you try to spin CNTs

  • into long fibers, their exceptional strength shrinks by 100 times. Now, I’m obviously

  • dubious whether CNTs will ever elevate us into space, but they can certainly conduct

  • electricity. That's because each carbon atom has a spare electron which can’t wait to

  • flow around. While MWCNTs conductivity isn't affected by the material geometry , SWCNTs

  • can have a metallic or semiconducting behavior based on the way the graphene layer is twisted,

  • a.k.a. the chiral angle. As a result, you can end up with a more or less conductive

  • configuration by design, like armchair, zig-zag, and chiral nanotubes. Again, you've got to

  • love the names ... armchair? Anyway, CNTs with an armchair structure are similar to

  • metals from the electric point of view. That’s why theyre the focus for making power cables.

  • But the challenge is being able to make these nanowires as long as possible.

  • Back in 2014, after years of lab work, researchers at Rice University *knitted* nanotubes into

  • a fiber that carried 4 times more current than copper. When filling a cable, these armchair

  • DWCNT wires can transfer power over longer distances while sustaining lower losses compared

  • to copper. You may see why their scale-up could make our grid so much more efficient.

  • But we have a *macro* problem. It’s very difficult to mass produce pure armchair CNTs,

  • which I'll get to in a minute.

  • Other than potentially improving grids, researchers have recently opened up a new *thread* for

  • CNTs: Making the most out of waste heat. Just think of sources like solar panels or power

  • plants.

  • But before I get into that hot carbon nanotube advancement ... let's talk about another hot

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  • Now back to the hot carbon nanotube advancement...

  • According to the US Energy Information Agency, over 60% of the energy used for generating

  • electricity in America is lost as heat. Well, apparently CNTs may be a good fit for recovering

  • this unused thermal power and upcycling it into renewable electricity. And there seems

  • to be a *common thread* in the innovators here. Once again, Rice University. After improving

  • power cables, Rice scientists used SWCNTs ... wait, rice scientists? I think that's

  • a completely different thing ... Rice University scientists used SWCNTs to make a waste heat-to-energy

  • device. Basically, they designed a carbon nanotubes film containing cavities that trap

  • the infrared heat from the sun and narrow its bandwidth. When doing so, they give off

  • photons, which can be efficiently converted into electricity. Researchers claim that integrating

  • their heat-recovery device within solar panels would boost their efficiency up to 80%. Compared

  • to solar panels available on the market today, which don't go above about 23%, that sounds

  • dramatic. But you'd need to compare those to the efficiencies in other lab solar cell

  • tests, which are around the 50% mark. So this claim still needs to be vetted and work its

  • way out of the lab.

  • Just this August Rice University researchers revamped their tailoring skills and released

  • their latest tubular collection ... a CNT-containing textile that turns heat into electricity.

  • This could set a new fashion trend in the green energy world. Donning their dressmaker’s

  • hats, scientists have used a sewing machine to craft a smart cloth out of DWCNTs fibers.

  • As it turns out, this tubular dress is a thermoelectric generator. Basically, it can convert sunlight

  • and other heat sources into electricity. During a lab experiment, jointly set up by Tokyo

  • Metropolitan University and Rice University Carbon Hub, this *supercharged* fabric used

  • the heat from a hotplate to turn on an LED light . It may not sound like a *powerful*

  • achievement to you, but this new CNT clothing line hit a record-breaking power factor which

  • is three times larger than the commercial standard.

  • But how does that work? Essentially, you generate electricity whenever there's a temperature

  • gradient across the material. Meaning that one side of it is hotter than the other. Funny

  • as it sounds, individual nanotubes hold a *giant* power factor. This is the energy density

  • you can get out of a material depending on a particular temperature difference. There

  • are two components affecting the power factor of a material. Its electrical conductivity

  • and the so-called Seebeck coefficient , a.k.a. thermopower, which gives you an indication

  • of how much electricity a material generates out of thermal variations. Imagine you join

  • two wires made of different metals and you heat up one of them. When you do that, electrons

  • will flow towards the cooler part of this circuit. Well, Seebeck was the first one to

  • *see* that, which is why this phenomenon is called the Seebeck effect. And it’s the

  • basic principle of how thermocouples work. So far, scientists have struggled to preserve

  • the CNTs power factor when weaving them together into a larger framework like a fabric ... until

  • now. The Rice group ... sorry, the Rice University group was the first at creating a large-size

  • CNTs-based structure that retains the superior energy density of the individual tubes.

  • They managed to pack the fibers into a dense and highly aligned pattern. This led to an

  • electrical conductivity over 10 times higher than those measured in the past for CNT macrostructures.

  • On top of that, designers played around with the CNTsFermi energy. This can be defined

  • as the difference between the highest and the lowest kinetic energy level of electrons

  • at 0 kelvin (ca. -460 F). At any other temperature, you refer to the Fermi level instead, which

  • is often called electrochemical potential. Now, I'm not a scientist, so if I missed anything

  • here, sound off in the comments. I know it all sounds complicated so let’s focus on

  • a keyword: kinetic. Adjusting the Fermi energy, or level, will affect how fast electrons move

  • throughout the material. In other words, the electric conductivity. A successful tuning

  • of this parameter allowed researchers to tweak the fibers' electronic properties. They doped

  • the textile with some chlorine-containing chemicals and achieved a higher Seebeck coefficient,

  • which means having a more efficient nanocouple.

  • Obtaining a very high power factor is crucial for energy harvesting applications because

  • you maximize the electricity output you get when tapping into renewable sources like solar

  • or industrial waste heat. For the sake of the experiment, scientists tested centimeters-long

  • fibers. However, researchers obtained the same electronic properties after plying the

  • smaller fabric pieces into longer CNTs threads, which means the product is scalable.

  • The major caveat here is that it's only been proved in the lab, but it's a very encouraging

  • result as energy-efficient CNT macrostructures will be essential to develop real-world energy

  • harvesting devices. And that’s what the research group is planning to develop further

  • in the future. A possible application would be active cooling of electronics. Thanks to

  • their high thermal conductivity, the nanotube fibers could draw heat out of sensitive optoelectronics

  • that may otherwise fail when exposed to high temperatures. While they haven’t disclosed

  • any funding from private investors, this research was supported by a few foundations as well

  • as by the US Air Force and Department of Defense.

  • Although these recent developments are *heating up* the vibes around CNTs, it’s taking ages

  • to commercialize these revolutionary materials. So, what’s been obstructing the tube between

  • the lab and the market?

  • The main challenge has been developing larger CNT-based structures that preserve the marvelous

  • properties of each of their building blocks. Another major conundrum has been selectively

  • growing a nanotube with a specific geometry. Whenever creating CNTs, you always end up

  • having a *cocktail of nano-straws* with different shapes and properties. And, most importantly,

  • this clumping mess doesn’t have the wondrous qualities of single CNTs. However, over the

  • last year or two researchers have come up with different methods to disentangle the

  • CNTs clustering issue.

  • One of scientistsmain goals has been to separate metallic and semiconducting tubes.

  • To achieve this, they developed different kinds of polymers to dissolve and wash away

  • one type while leaving the other one behind. Another team of researchers used cresol, an

  • ingredient of commercial cleaning products, to purify the CNTs jumble. In addition to

  • avoiding harsh chemicals that could reduce CNTs conductivity, using cresol gave the isolated

  • tubes a sticky twist. As researchers increased the amount of cresol, their purified product

  • changed consistency from toothpaste-like to gel to a sort of charcoal dough that basically

  • behaves like plastic. This is still in the lab phase, so more testing and development

  • is happening, but their polymer-like creation could bring massive practical advantages.

  • It'd be much easier to handle and carry around compared to fluffy carbon powders. And they'd

  • be more suitable for composite industrial production.

  • After 30 years, CNTs pioneer Sumio Iijima hasn’t lost his early enthusiasm and is

  • still trying to accelerate carbon nanotubes mass production. Apparently, he filed a patent

  • for a new method that would tidy up the CNT mess you normally get. All these contributions

  • could make life easier for the few companies who are working hard to commercialize them.

  • Like Huntsman Corp, which has been able to increase production from a gram an hour to

  • being able to create a kilogram an hour. That's a 1000 times increase in a few years and they're

  • continuing to scale it up.

  • The hype on carbon nanotubes isn't as high today as it was 30 years ago, which is a good

  • thing. I think the expectations are more realistic now. But theyre still some of the most

  • promising materials for the future of green technologies. While manufacturing CNTs at

  • scale has worked out to be far more complex and time-consuming than expected, researchers

  • have made significant, albeit slow, progress. Clearly, they still can’t promise us a space