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Large Sheets of Carbon Nanotubes Produced
StCredZero brings news that scientists have developed sheets of nanotubes that measure up to three feet by six feet, and they promise "slabs 100 square feet in area as soon as this summer." The developers see uses for the sheets in electromagnetic shields and airplane construction, and according to the Next Big Future blog, the sheets could also impact the development of solar sails.
"The sheets, which the company can produce on its single machine at a rate of one per day, are composed of a series of nanotubes each about a millimeter long, overlapping each other randomly to form a thin mat. The tensile strength of the mat ranges from 200 to 500 megapascals--a measure of how tough it is to break. A sheet of aluminum of equivalent thickness, for comparison, has a strength of 500 megapascals. If Nanocomp takes further steps to align the nanotubes, the strength jumps to 1,200 megapascals."
If this stuff is as strong as aluminum, why aren't we using it to actually build things like cars and buildings?
Because they are just learning how to create and manipulate such materials? Your question is like a bronze age smith who knows that small bits of iron can be found and worked saying "How come we haven't replaced bronze with this stuff yet?" It's an engineering challenge is all. As production techniques improve it will be easier and cheaper to make.
Also, note that it's just the tensile strength that is comparable to aluminum. They said nothing about it's shear strength or rigidity.
Perhaps aluminum is soft among metals and ceramics, but a large sheet of carbon with this kind of tensile strength is pretty novel.
http://hyperphysics.phy-astr.gsu.edu/Hbase/tables/elabund.html
Aluminum makes up 8% of the Earth's crust. The earth's composition of carbon appears to be much lower, the same page shows it's 0.03% of the earth's total weight. That doesn't say much of how easy it is to collect either resource, but abundance doesn't seem to be the answer. I think it's the strength-to-weight ratio that makes carbon nanotube materials interesting, but it's still pretty expensive to make.
It depends a lot on the properties of the material. For example, while aluminum sheets are made of microscopic crystals, there is little danger of breathing significant amounts of aluminum unless you spend a lot of work processing it into a fine powder first. These sheets may be the same way. Who knows? We don't.
Yes, AND they'll want to use aluminum foil to cover the leftovers.
.sig withheld by request
and it's within 2 orders of magnitude to get there. Not too bad. Shouldn't be too hard to engineer, or tweak it to get there.
..........FULL STOP.