Graphene will protect from better bullets
Recall that graphene was discovered relatively recently. This is a monatomic carbon layer that has a unique set of properties and characteristics, in particular, record-breaking thermal conductivity and strength. For the first time this material was synthesized in 2004 by physicists of Russian origin Konstantin Novoselov and Andrey Geim, who at that time worked in the UK. In 2010, both scientists shared the Nobel Prize in Physics for their discovery. In the 2011 year, both the academic decree of Queen Elizabeth II was awarded the title of Knights Bachelor for services to science, which gives them the right to add to his name the title "Sir".
The monatomic carbon layer discovered by scientists can work wonders and is already recognized by many materials of the future. Graphene is stronger and lighter than any materials known to us, it conducts electricity ten times better than theorists assumed, and is also capable of preventing the process of metal corrosion. Almost every day, scientists discover some new properties of this unique material, which makes it possible to expand the range of possible use of graphene in the future, when its high-grade industrial production is established.
Today, graphene is produced mainly in scientific laboratories and only in small quantities. The main method of graphene production that exists today is based on mechanical peeling or detachment of graphite layers from highly oriented pyrolytic graphite. This method allows scientists to obtain the highest quality material samples with high carrier mobility. However, this method does not involve the use of large-scale industrial production, since it is manual labor. So far, this technique has not been significantly improved, although work is being done in this direction. For this reason, graphene sheets are still a very expensive material and relatively small in size.
A team of scientists led by Thomas Edwin of the University of Rice conducted research and found that graphene has a very high, one might say exceptional, resistance to microscopic high-speed "bullets." According to American scientists, graphene has demonstrated an excellent ability to dissipate the impact energy. The material was 10 times stronger than the best to date have become and 2 times stronger than Kevlar. The results of the research of scientists were published in the specialized scientific publication Science.
In the course of the experiment, scientists from Rice University bombarded multi-layer graphene membranes with thicknesses from 10 to 100 nm (this is approximately from 30 to 300 graphene layers) using tiny silicon dioxide spheres. These graphene membranes were produced by a classical mechanical method: by removing graphene flakes from pieces of pyrolytic graphite. In order to test the stability of graphene on such tiny samples, it was decided to use a non-standard gunshot weapon, and a special technique based on a laser. The laser beam evaporated a thin film of gold with a thickness of approximately 50 nm, as a result there was an explosive expansion of the gas, which accelerated the silicon “bullet” to a speed of about 600 m / s. For how the graphene membrane reacts to such a blow, the scientists observed with a powerful electron microscope.
During the impact, graphene experienced conical deformation: in a stack of graphene sheets, a silicon sphere formed a funnel. In this case, in the upper layers, the formation of radial cracks occurred, which went in directions approximately corresponding to the corners of the crystal lattice of this material. Analysis of the results showed that at the places where the “bullets” hit, the graphene sheets were simply pulled into a cone, spreading the impact energy along the lines of the crystal lattice of the material. That is, the energy spread in the most resistant to tearing directions. In the case of penetration, along these lines cracks formed, which diverged in a circle at a certain distance from the place of impact of the “bullet”. In addition, it was found that graphene sends part of the kinetic energy back into the “bullet”, due to which the graphene sheets dissipate the impact energy much more efficiently than steel.
Speaking in terms of numbers, graphene is able to absorb energy on the order of 0,92 MJ / kg, while steel under comparable conditions usually absorbs on the order of 0,08 MJ / kg. The ability of graphene to effectively dissipate energy, scientists explain the high degree of rigidity in combination with a low density of the material. This means that energy can move through the material very quickly, while its effective absorption and dissipation into space takes place.
The fact that graphene is the most durable material in the world, exceeding even diamonds in strength characteristics, has been known to scientists before. But the ability of resistance of such armor "bullets" was proved only now in the entrance of the experiment. According to one of the co-authors of the study, Edwin Thomas of the University of Reis, graphene layers are able to quickly dissipate the impact energy, before they collapse. Scientists note that a similar effect in graphene is observed only until the speed of the released “bullets” at the moment of their impact with the material reaches the speed of sound in the material. At the same time, inside a light graphene, the speed of a sound wave can reach 22 km / s, in contrast to all 332 m / s in the air.
The unique protective properties of graphene discovered by scientists resemble those that can be observed in ceramic armor. Ceramic armor is also able to actively absorb impact energy due to the destruction of the high-strength molecular lattice. Scientists believe that a possible combination of graphene and ceramics will help in the future to create lightweight, heavy-duty armor that can be used in the production of body armor. Such an armor with a weight in 1-2 kilogram would protect the soldier even from armor-piercing rifle bullets. According to scientists, the open armor properties of graphene can be useful to mankind in space: to protect satellites and other spacecraft, such as the ISS, probes, as well as advanced interplanetary ships as they move in the dangerous "littered" corners of our solar system, to which the Belt can be attributed Kuiper.
The latest discoveries of scientists allow in the future to increase the possible options for the practical use of graphene, but they cannot solve the problem of the complexity of its manufacturing process and its high cost. But even in spite of this, the use of such expensive material and technologies based on it can be fully justified when it comes not to producing mass commercial products (the same body armor), but to unique items, for example, for the same space industry.
Information sources:
http://zoom.cnews.ru/rnd/news/top/grafen_zashchishchaet_ot_gisperskorostnyh_pul_luchshe_stali
http://www.vesti.ru/doc.html?id=2159071&cid=2161
http://naked-science.ru/article/sci/graphene-bulletproof
http://gearmix.ru/archives/16591
Information