Tag Archives: graphene

Isn’t graphene even more fun? Carbon chainmail

Thought for the day:

graphene

Graphene, picture from cnx.org

 

chainmail

A Chainmail structure, picture from 123rf.com

It’s a bit easier to see how the links overlap in this pic:

colour chainmail

 

pic from mediafocus.com

So, just thinking out loud, perhaps the rings in the chainmail above could be rings of carbon, just 6 atoms each. If so, would this be better than graphene at anything useful, or not? Would longer rings work better? The idea of carbon nanotube chainmail is about a decade old.

Carbon chainmail

 

Powerpoint really is not designed as a proper drawing tool and not having a week to spare, I didn’t bother doing the link overlaps or even the bonds properly in my pic, but together with the other two, I think you will get the idea fine.

I don’t know if this will work or not, but it might be an idea worth looking at further.

 

 

 

Isn’t graphene fun?

I’ve just been checking up on progress on supercapacitors to see if they are up to the job of replacing car batteries yet. It looks like they will be soon. Supercapacitors have lower energy density than lithium batteries, but can be charged extremely quickly.

My favoured technique is to build mats into the road surface every 50 metres (i.e. same as streetlights), and to charge the supercapacitor bank using induction as the car passes over them. That means that even a small energy capacity would be adequate. It wouldn’t have to power the car for 100 miles or more like a battery, but only for the first and last few kilometres of a journey where there are no mats. Otherwise, range wouldn’t be limited as it would charge all the time on the trip.

However, a few minutes ago I had another little spark of enlightenment. Why not also use the pads for propulsion too, using a linear induction motor?  (I like those)

If the pad gives an impulse to the car as well as a capacitor recharge, then the capacitor won’t need to be as big. And if the impulse is gentle enough, passengers won’t feel a jolt every time they drive over one.

Another little insight, hardly worthy of the name, is that with trains of self driving pods, the pods could be so close together on most journeys that they effectively have a continuous circuit from one end of the train to the other. That means that public transport pods that are only used locally and on certain routes might be able to get by with tiny capacitor banks.

Super-tall (30km) carbon structures (graphene and nanotube mesh)

I recently blogged about a 200km moon-based structure. Here is my original earth-based concept, which could now be enhanced by filling columns with graphene foam

http://timeguide.wordpress.com/2013/01/05/could-graphene-foam-be-a-future-helium-substitute/

How about a 30km tall building? Using multilayered columns using rolled up or rippled graphene and nanotubes, in various patterned cross sections, it should be possible to make strong threads, ribbons and membranes, interwoven to make columns and arrange them into an extremely tall pyramid.

Super-tall structures for science and tourism

Think of a structure like the wood and bark of a tree, with the many tubular fine structures. Engineering can take the ideas nature gives us and optimise them using synthetic materials. Graphene and carbon nanotube will become routing architectural materials in due course. Many mesh designs and composites will be possible, and layering these to make threads, columns, cross members with various micro-structures will enable extremely strong columns to be made. If the outer layer is coated to withstand vacuum, then it will be possible to make the columns strong enough to withstand atmospheric pressure, but with an overall density the same as the surrounding air or less. Pressure is of course less of an issue higher up, so higher parts of the columns can therefore be lighter still.

We should be able to make zero weight structures in lower atmosphere, and still have atmospheric buoyancy supporting some of the weight as altitude increases.  Once buoyancy fails, the structure will have to be supported by the structure below, limiting the final achievable height.  Optimising the structures to give just enough strength at the various heights, with optimised mesh structure and maximal use of buoyancy, will enable the tallest possible structures. Very tall structures indeed could be made.

So, think of making such a structure, with three columns in a triangular cross-section meeting at 43 degrees at the top (this is the optimal angle for the strongest A frame in terms of load-bearing to weight ratio, though that is a simplistic calculation that ignores buoyancy effects, so it ‘needs more work’.

Making a wild guess, 30km tall structures may be feasible, but that is just a wild guess and I would welcome comments from any civil engineers or graphene architects. These would not be ideal for habitation, since most of the strength in the structure would be to support the upper parts of the structure itself and whatever platform loading is needed. The idea may be perfect for pressurised platforms at the top for scientific research, environmental monitoring, telescopes, space launches, tourism and so on. The extreme difference in temperature may have energy production uses too.

Getting the first 30km off the ground without needing any rocket fuel would greatly reduce space development costs, not to mention carbon and high altitude water emissions.

A simple addition to this would be to add balloons to the columns at various points to add extra buoyancy. I dare not try to calculate how much higher this would permit, but I suspect not all that much more since even with balloons, they cannot give much extra lift once the atmosphere is too thin.

Could graphene foam be a future Helium substitute?

I just did a back-of-the-envelope calculation to work out what size of sphere containing a vacuum would give the same average density as helium at room temperature, if the sphere is made of graphene, the new one-size-does-everthing-you-can-imagine wonder material.

Why? Well, the Yanks have just prototyped a big airship and it uses helium for buoyancy. http://www.dailymail.co.uk/sciencetech/article-2257201/The-astonishing-Aeroscraft–new-type-rigid-airship-thats-set-revolutionise-haulage-tourism–warfare.html

Helium weighs 0.164kg per cubic metre. Graphene sheet weighs only 0.77mg per square metre. Mind you, the data source was Wikipedia so don’t start a business based on this without checking! If you could make a sphere out of a single layer of graphene, and have a vacuum inside (graphene is allegedly impervious to gas) it would become less dense than helium at sizes above 0.014mm. Wow! That’s very small. I expected ping pong ball sizes when I started and knew that would never work because large thin spheres would be likely to collapse. 14 micron spheres are too small to see with the naked eye, not much bigger than skin cells, maybe they would work OK.

Confession time now. I have no idea whether a single layer of graphene is absolutely impervious to gas, it says so on some websites but it says a lot of things on some websites that are total nonsense.

The obvious downside even if it could work is that graphene is still very expensive, but everything is when is starts off. Imagine how much you could sell a plastic cup for to an Egyptian Pharaoh.

Helium is an endangered resource. We use it for party balloons and then it goes into the atmosphere and from there leaks into space. It is hard to replace, at least for the next few decades. If we could use common elements like carbon as a substitute that would be good news. Getting the cost of production down is just engineering and people are good at that when there is an incentive.

So in the future, maybe we could fill party balloons and blimps with graphene foam. You could make huge airships happily with it, that don’t need helium of hydrogen. 

Tiny particles that size readily behave as a fluid and can easily be pumped. You could make lighter-than-air building materials for ultra-tall skyscrapers, launch platforms, floating Avatar-style sky islands and so on.

You could also make small clusters of them to carry tiny payloads for espionage or terrorism. Floating invisibly tiny particles of clever electronics around has good and bad uses. You could distribute explosives with floating particles that congeal into whatever shape you want on whatever target you want using self-organisation and liberal use of EM fields. I don’t even have that sort of stuff on Halo. I’d better stop now before I start laughing evilly and muttering about taking over the world.

200km tall base for the lunar elevator

I was 8 when Armstrong and Aldrin set foot on the moon. It was exciting. My daughter is 18 and has never witnessed anything of the same order of excitement. The human genome project was comparable in some ways but lacked the buzz. Ha ha!

There is excitement about going back now. We will, and on to Mars. We can do space so much more safely now than back in the 60s.  Commercial companies are pioneering space tourism and later on will pioneer the mining bits. But the excitement recently is over the space elevator. The idea is that a cable can stretch all the way from the surface out into space, balanced by gravity, and used as a means to cart stuff back and forth instead of having to use rockets, making it easier, less expensive and less dangerous.

It will happen eventually on Earth. We need to make new materials that are strong enough. Carbon nanotube cables and other fancy materials will be needed that we can’t make long and strong enough yet. But the moon has lower gravity so it is much easier there and will likely happen earlier.

Nextbigfuture has a nice summary: http://nextbigfuture.com/2012/08/unlike-earth-space-elevators-lunar.html and the NASA document is at http://www.spaceelevator.com/docs/iac-2004/iac-04-iaa.3.8.3.07.pearson.pdf

So I don’t need to repeat everything here. Instead, I am wondering about applying a derivative of my idea for a 30km tall building: http://nvireuk.com/2012/02/12/super-tall-30km-carbon-structures/

A 30km tall building on Earth could make use of atmospheric buoyancy for the lower end, which of course we wouldn’t get on the moon. But we also wouldn’t get wind on the moon to add stresses. And on the moon gravity is less so the structure could be much taller. On the moon a graphene structure could form as much as the bottom 150-200km of the climb. It might offer a nice synergy. Or perhaps it is just easier to add 200km to the elevator cable. I don’t know, and no longer have the maths ability to calculate it. Maybe worth a look though.