Posts Tagged‘material’

Stanene: Graphene’s Metallic Brother.

Graphene has proven to be a fruitful area of scientific research, showing that atom thick layers of elements exhibit behaviours that are wildly different from their thicker counterparts. This has then spurred on research into how other elements behave when slimmed down to atom thick layers producing such materials as silicene (made from silicon) and phosphorene (made from phosphorous). Another material in the same class as these, stanene which is made from an atom thick layer of tin, has been an active area of research due to the potential properties that it might have. Researchers have announced that they have, for the first time, created stanene in the lab and have begun to probe its theoretical properties.

will2dtinbetNot all elements have the ability to form these 2D structures however researchers at Stanford University in California predicted a couple years ago that tin should be able to form a stable structure. This structure then lent itself to numerous novel characteristics, chief among them being the ability for an electric current to pass through it without producing waste heat. Of course without a real world example to test against such properties aren’t of much use and so the researchers have spent the last couple years developing a method to create a stanene sheet. That research has proved fruitful as they managed to create a stanene layer on top a supporting substrate of bismuth telluride.

The process that they used to create the stanene sheet is pretty interesting. First they create a chamber that has a base of bismuth telluride. Then they vaporize tin and introduce it into the chamber, allowing it to deposit itself onto the bismuth telluride base. It’s a similar process to what some companies use to create synthetic diamonds, called chemical vapor deposition. For something like stanene it ensures that the resulting sheet is created uniformly, ensuring that the underlying structure is consistent. The researchers have then used this resulting stanene sheet to test the theoretical properties that were modelled previously.

Unfortunately the stanene sheet produced by this method does not appear to have the theoretical properties that the theoretical models would indicate. The problem seems to stem from the bismuth telluride base that they used for the vapor deposition process as it’s not completely inert. This means that it interacts with the stanene sheet, contaminating it and potentially disrupting the topological insulator properties which it should exhibit. The researchers are investigating different surfaces to mitigate this effect so it’s likely that we’ll have a pure stanene sheet in the not too distant future.

Should this research prove fruitful it could open up many new avenues of research for materials development. Stanene has properties that would make it extremely ideal for use in electronics, being able to dramatically increase the efficiency of interconnects. Large scale implementations would likely still be a while off but if they could make the vapor deposition process work then there’s immediate applications for it in the world of microelectronics. Hopefully the substrate issue is sorted out soon and we’ll see consumerization of the technology begin in earnest.


Fire Ants Exhibit Some Fascinating Properties in Large Groups.

Natural selection has given rise to some incredible things. The diversity of life on Earth is an ongoing testament to that, showcasing that life can sustain itself pretty much anywhere so long as there’s water present. What’s incredibly interesting to see is how parts of nature take on properties of things you wouldn’t necessarily think they would, like the planthopper with gears in its legs. It seems the more we investigate life here on Earth the more weird and wonderful behaviour we come across and none seems to be more stranger than the hive mentality of fire ants giving rise to a substance that’s neither liquid nor solid:

The research paper that this comes from is quite interesting as they performed a whole bunch of materials tests on the fire ants to see what the properties of the giant ball were like. Interestingly the fire ants, whether they’re alive or dead, exhibit properties of non-Newtonian fluids, specifically shear thinning (like when paint doesn’t drip off a brush). However the characteristics of the live fire ant ball don’t directly classify it as either a solid or a liquid although a similar non-live sample acted much more like a solid. That interesting property is most likely due to the way the ants rearrange themselves in response to stress but the actual mechanism of how they do that, especially in large numbers, is still something of a mystery.

It seems that this behaviour likely arose out of a particular selection pressure, namely flooding. The fire ants can bind themselves together in a ball or mat to form a raft that will float on water thanks to the large surface area relative to the fire ants weight. It’s the same principle that allows water skimmers and other insects to seemingly float on top of water, using the surface tension to provide them with buoyancy. The material properties that fire ant ball carries with it are likely a side effect of that adaptation, although there might be other pressure that led to it as well.

I’d totally go out and try this for myself but I value my hands far too much.