Tuesday, June 23, 2009

Higher temperature superconductors

I'm posting this prediction here because the Long Bet Foundation charges money to make a bet.

I think there will be another generation of superconductors pretty soon, say 3-10 years. I think this because of a trend I noticed with the discovery of type II superconductors in 1987 combined with a current trend in more sophisticated multiwalled nanotube production.

Up until the discovery of that first ceramic superconductor, superconductivity had only been achieved within about 30 degrees of absolute zero. Typically some very pricey liquid helium was used to get a material down to the appropriate temperature range. And the superconductivity effect occurred in all 3 dimension.

With the invention of a ceramic (or perovskite) superconductor, there was a huge jump in critical temperatures. Pretty soon superconductivity could be found at temperature over 110 degrees Kelvin. But the superconductivity occurred in a planar fashion, a reduction in dimensionality from 3 to 2. I visualize this as something akin to a layer cake where a middle layer is the site of zero resistance. It seemed to me like we traded a decrease in dimensionality for an increase in temperature.

So the next logical step is to go from 2 dimensions to one dimension, with a corresponding increase in temperature. Since the type II superconductors are like a 'tuning' of layers to get one special layer with the superconductivity behavior, then these new superconductors will be layered cylinders where the layers are 'tuned' to create a single dimension of superconductivity. Which seems similar to the various multiwalled nanotubes I keep reading about in the science journals. And since the researchers are riding an improvement curve for engineering the layers of multiwalled nanotubes, it seems likely that even the probably rare mix of chemistry and structure that could result in a linear superconductivity will be stumbled upon soon.

I have been expecting that higher temperature superconductivity in multiwalled nanotubes would be sited along the axial center, but I suppose it could also occur in one of the inner walls of the nanotube, a bit away from center. Since the pairing of electrons into Cooper Pairs involves a certain range of distances, perhaps the superconductivity occurring a layer or two out from the center would actually be a critical requirement.

The net result could be superconductivity at temperatures much easier (and cheaper) to achieve, perhaps even at room temperature. If we could get superconductivity at dry ice or even water ice temperatures, then lots of applications become possible, or at least cheaper: lossless power transmission, cheaper maglev, cheaper medical scanning, almost noiseless information transfer, lossless energy storage.

I think the sustainability movement could benefit greatly from the potential efficiencies in electrical transmission and particularly energy storage. When one inserts a current into a superconducting ring, orbits the ring for as long as the superconducting state is maintained. If the nanotube superconductors could be made cheaply enough and with a pretty high tolerance for magnetic fields, then we might solve the green energy industry's major hurdle of storage.

Right now the type II superconductors are often cooked up via crystal growing and epitaxial deposition, a process I've had some experience with. I'm not sure what percentage of type II's are fabricated this way, but I am sure that all of the processes used are fairly demanding in energy, materials (due to the rare earth elements involved) and labor, and are therefor costly. For the hypothetical nanotube superconductors, the fabrication processes might be more akin to electroplating, at a great reduction in energy and time costs. It would be a bit ironic but certainly convenient if the newer, better superconductors were also cheaper and easier to scale up in fabrication.

I am interested to hear if anyone has some theory or data to support or preclude this possibility.


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