TALK ABOUT Predator and Cloaking

Graphene, the super two-dimensional material, has some outstanding properties. It is 200 times stronger than steel by weight, and it can conduct heat and electricity with ease.

But graphene might not be alone in the elite two-dimensional structure ranks for much longer, as it could soon be joined by its cousin: Stanene. This new compound on the block has some exciting and versatile properties that might just give graphene a good run for its money.

The compound was hypothesized two years ago, and researchers at Shanghai Jiao Tong University think that they have succeeded in making it. The results can be found in Nature Materials. Stanene is a two-dimensional compound. It has similarities to graphene, but instead of carbon atoms, stanene is composed of tin atoms. The tin creates a six-sided honeycomb structure, not dissimilar to graphene, that can be discerned at the nanoscale.

The layer is supported by a structure composed of atoms of bismuth telluride, which can be seen in the side view of the following diagram. 

Front and side view of stanene’s structure (red and blue) resting atop a supporting compound (cyan and gray). Feng-feng Zhu et al./Nature Materials.

But what makes stanene extra special? In theory at least, it has some properties that would make it especially suited to conducting electricity without wasting much energy creating heat. Electrons race down the edges of the stanene layer, bypassing the central lattice. As a result, they don’t squander valuable energy interacting with other particles, which means that this material has potential applications in devices in many other fields. These conclusions come from predictions made back in 2013 by Shou-Cheng Zhang, the coauthor of this new stanene study.

It is currently inconclusive that stanene has been created, according to other scientists. While the results so far are promising, with the distance between the layers of atoms consistent with the predictions, it will be clearer whether stanene has been created when scientists have the opportunity to image it using techniques such as X-ray diffraction. Unfortunately, these procedures require more stanene than the scientists have currently grown, so it will be some time before enough stanene can be made for these sorts of conclusive tests to be carried out.

However, the evidence so far is promising. So far, stanene is looking like the next big thing in two-dimensional materials. Let’s hope that the reality will be able to live up to the hype.

Central Image: Stanene at the nanoscale with a discernible honeycomb structure. Feng-feng Zhu et al./Nature Materials.

METAMATERIALS

What about invisibility or cloacking technology? In 2015 scientists designed a very very thin material about 80 nanometers thick, that could hide equally tiny objects. In order for us to see an object light has to bounce off of it and any distortion of that light reveal it’s shape and features. This invisibility material uses teny tiny brick shaped gold antennas to counteract that natural light distortion. So when this cloack is wrapped around an object any light bouncing off of it looks like it’s coming froma perfectly flat mirror, hiding the fact that the cloack and object are even there. Theoretically you could even adjust the gold antennas to make the reflected light look like any object or background. This technology only hides microscopic objects right now so scientists need to figure out how to scale up the idea before we could use the cloaking technology on larger objects, like soldiers.

These nanostructures are the smallest part yet they make a huge impact. The prefix nano means something really small, like 10 to the negative 9 small. 0.000000001 centimeters. Nano has been oaired with materials, bots, optics and other super clicky topics, scientists and engineers are working tirelessly to build nanostrucutes. Because of the physics advantages of these projects. In 2016 the journal nature materials published a paper detailing the smallest lattice structure ever created by humans. This is important because building things at these tiny scales hack the laws of physics. Creations like these are called metamaterials because even though it’s made of carbon, it has properties that are way different than the normal material. In this case the strength to densioty ratio is 6 times higher than previously created materials. Engneers and scientists think they could use this new metamaterial for batteries or other electrochemical purposes. Metamaterials are basically specifically arrangements of plastics or metals that take advantage of a tendancy hidden in those elements, usually regarding the electromagentic spectrum. For example, the reason you can see trees is because they’re made of atom that wasn’t speicifcally arranged. But with the right design a metamaterial could reroute electrical waves around an object, this is called negative refraction, which gives the illusion of invisibility. It was predicted by russian physicist Victor Vesilago in teh 1960s and since the founding of metamaterials as a field of nanotechnology, it has been covered ad nauseum as a possible technological harry potter or predator invisibility cloak.

The promises that in the coming decades with carbon nanotubes, with graphene, will create even new substances which can replace the silicon of computers, maybe even give us a space elevator. Graphene is a substance made of a one molecule thick layer of carbon atoms . That graphene is so strong in principle you can put the elephant on a pencil, suspend the elephant on the pencil, put the pencil on the sheet of grapnehe, and the graphene will not break. It is the strongest material known to science at the present day. Graphene is a one atom thick, perfect electrical capacitor. Roll it into tubes, it becomes super strong carbon nanotubes. Layer it with copper and you get a metamaterial. A highly engineered structure that is 500 times stronger than the pure metal itself. The best part is that this graphene can be printed with a regular inkjet printer. Thanks to researchers at the university of Utah, metamaterials can be created using regular 4 color inkjet printers loaded with carbon and silver ink. Using that researchers were able to build 10 different sample prototypes in a fraction of the time of traditional manufacturing. The materials can be tested against terrahertz waves to ensure that they block and reflect them just right. The researchers were pumped that office equipmetn can create super intricate plasmonic metamaterials. The researchers say the ability to create these prototypes might revolutionize the engineering of wireless data transmission, magnetic materials, the sensing of biological weapons, and even space craft insulation. There are several different approaches that scientists use to hide an object. One technique involves bending light to mask the object. Another method is to render an object virtually transparent to microwaves, by using metamaterials, which are basically lab mad materials not found in nature to prevent the waves from scattering after contacting the object in question. Though the effect created by these metamaterials isn’t quite transparent enough yet.

VANTABLACK

Another approach to invisibility is making something so dark that the human eye can’t actually see it, especially at night. The Natural Physical Laboratory in the UK have recently invented the darkest material known to man called Vantablack. It is darker than the blackest of blacks, it is so dark that almost no light can escape it. It’s absorbed 99.965% of photons that hit it. It’s made from carbon nanotubes that trap any light that hits them. It’s so dark that you can’t even see how fdark it is because your computer monitor is not capable of reproducing such a dark black. If you cover any object with vantablack it immediately removes any 3d ness from it, turning it into a completely 2d black spot, blending into the horizon in the night sky. For this reason, the military is ordering it in vast quantities to make armor for shocktroopers, they are suspected to use it to cloack military aircraft and naval vessels at night.

What if you could see the complete absence of light? the darker something looks the more light its absorbing and the less it’s reflecting back at your eyes. So a black hole which absorbs 100% of all light is the darkest thing possible, but you’ll never see a black hole in person. A new material clled vantablack is pretty close to complete and total darkness. And this stuff is freakylooking. Back in 2012 the british company Surrey nanosystems started developing Vantablack. A coating that’s made to absorb as much light as possible. The first version of vanta black released in 2014 absorbed 99.965% of all visible light that hit it. In march of 2016 the company announced that it created a new version of vantablack called vantablack 2, it absorbs so much light that they can’t even measure how much it’s absorbing. With either version of vantablack so little light gets reflected that your eyes can’t figure out what they’re looking at. A black chalkboard reflects 7% of the light that hits it, so you can see the natural texture. You can see the bumps and cracks on asphalt becuase it still reflects 4% of light hits it. An object coated with vantablack on the other hand, reflects so little light that all of it’s surface details vanish. Even crumpled up aluminum foil looks flat when coated with vantablack. The VANTA stands for Vertically aligned carbon nanotube arrays, which makes sense since the material is made of hollow carbon nanotubes 1 meter in diameter. It’s made with specially designed chamnber and heat lamps which raise the temperature to above 430 degrees celsius. Each carbon nanotube or CNT is 10 thousand times thinner than a human hair. So small that photons, the particles that make up light, can’t get inside the tubes. But 99 % of Vantablack is actually just free space. Light goes between the tubes where it gets trapped and turned into heat, in other words, it’s absorbed. A material that absorbes almost all light has huge implications in the military. Vantablack is also incredibly strong, in the sense that it can resist the vibration and shock of a rocket launch so it can be used as a coating for military aircraft or spacecraft. There is a spreay on form of vantablack put it has to be applied by a specialist. f it’s not applied in just the right way the material in the spray won’t bind together and the coating won’t work properly. Anything coated by the material looks 2 dimensional, so it can any depth of movement for military troops moving at night.

PENTAGRAPHENE

Graphene is a monolayer of carbon atoms arranged in a honeycomb pattern that is incredibly light, flexible, and strong. A new study published in the Proceedings of the National Academy of Sciences from senior author Puru Jena of Virginia Commonwealth University describes a new structural arrangement of carbon. Instead of carbon atoms arranged in hexagons, the pattern is made out of pentagons. Very aptly, the theoretical material is being called penta-graphene. In the future, this could have a wide range of implications.

“The three last important forms of carbon that have been discovered were fullerene, the nanotube and graphene. Each one of them has unique structure. Penta-graphene will belong in that category,” Jena said in a press release.

Street tiles in Cairo are composed of pentagons, and a painting depicting that arrangement caught the eye of co-author Qian Wang while she was out eating dinner with her husband. Ever the scientist, she was immediately inspired by the pattern.

“I told my husband, “Come, see! This is a pattern composed only of pentagons,'” Wang recalled. “I took a picture and sent it to one of my students, and said, ‘I think we can make this. It might be stable. But you must check it carefully.’ He did, and it turned out that this structure is so beautiful yet also very simple.”

The penta-graphene was then synthesized with computer modeling. Analysis of the material revealed that it is very stable and will not rearrange without external manipulation, and that it is strong and can bear temperatures up to 1,000 Kelvin (1,340 °F).

There are also certain situations in which penta-graphene could outperform standard graphene. Graphene lacks a bandgap that allows it to act as a semiconductor without making structural changes that compromise its strength, but penta-graphene appears to function as a reliable semiconductor in multiple orientations.

“When you take graphene and roll it up, you make what is called a carbon nanotube which can be metallic or semiconducting,” Jena explained. “Penta-graphene, when you roll it up, will also make a nanotube, but it is always semiconducting.”

While the computer modeling readily shows that this pattern has a number of desirable attributes, the next step isn’t going to be quite as easy. Taking a computerized pattern and synthesizing it into an actual material has not been attempted yet, and there isn’t a clear approach to take. However, the researchers are very optimistic about the potential of the design.

“Once you make it, it [will be] very stable. So the question becomes, how do you make it? In this paper, we have some ideas,” Jena explained. “Right now, the project is theoretical. It’s based on computer modeling, but we believe in this prediction quite strongly. And once you make it, it will open up an entirely new branch of carbon science. Two-dimensional carbon made completely of pentagons has never been known.”

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