"Research charcoal Weng said carbon" (III): I fooled?-Talk about the strength of graphene

Originally, Yan Tan Weng said that carbon (III) wanted to write“What is carbon?”However, on the Internet, several commentators commented on the previous article.“Research on carbon (II) and graphene”(hereinafter referred to“Previous”) The comparison and examples of graphene strength are questioned. Visitors to Jiaotong University steel researchers even unceremoniously put forward:“Is this a scholar? Why does it look like a hoax?”. Therefore, I was forced to write this article first as a general reply.

When writing popular science articles, in order to avoid boring numbers and too deep theoretical exposition, simple comparisons and examples are often used to illustrate, hoping to achieve the purpose of explaining the profound and simple.“Previous”The comparisons and examples mentioned in are not original but quoted from other articles (because they are popular science articles, of course, no references are listed), but these comparisons and examples are based on theoretical and experimental data. The examples and comparisons or metaphors of popular science articles cannot be as accurate and relevant as those of scientific papers, but they must not be as completely outrageous as those of science fiction. So, how strong is graphene,“Previous”Are the examples and comparisons in outrageous? Is the author of the article bluffing??

outer layer electron formationsp²The carbon-carbon double bond formed by the hybrid carbon atom (C = C) is one of the strongest valence bonds in nature, according to its bond energy607KJ/moland the density of carbon bonds, the elastic modulus of graphene is calculated1Tpa(1 TPa = 103 GPa = 106 MPa). According to Gieraman (Gipage) The calculation of the theoretical inherent strength of solid materials can be obtained, and the tensile strength of graphene is180GPa. When it comes to steel, it generally refers to massive steel, including various grades of carbon steel and stainless steel, and its strength is in0.78-1.68GPaBetween, Graphene is not stronger than they are100How many times more?

I am a scholar with shallow knowledge and little knowledge. I only know a little about carbon. I really don't know that piano wire and steel whisker have such high strength. This also shows the truth that interlacing is like a mountain. However, there is no ignorance to compare graphene with steel wire or steel whisker! If the theoretical strength of steel is20GpaHowever, massive steel should be the same as ordinary massive carbon materials, it is difficult to achieve the tensile strength level of fibers and whiskers, let alone achieve its theoretical value. In addition,“Previous”Also did not say that graphene is the theoretical strength of steel100Times!

Single-layer graphene is a perfect ideal crystal, and its mechanical properties can be close to its theoretical value,SP²The measured tensile strength of carbon nanotubes formed by hybrid carbon-carbon bonds also has150Gpa(SeeNature. 1997.vol. 389.no. 6651,pp,582-4). The tensile strength of the graphite whiskers is21 GPa. Carbon fibers are also mainly used.SP2Although the material formed by the hybrid carbon-carbon bond is affected by many factors such as cracks, pores and grain size in brittle materials, its tensile strength is far from the theoretical value, but the tensile strength value of its industrial products is also quite high.T300,T800andT1000The tensile strength can reach respectively3.5GPa,5.5Gpaand7.0GPa. These are also visible, tangible and have been widely used in aviation, aerospace, military and other departments. It is because of the high strength and high modulus of carbon fiber that the U. S.F-22The surface of fighter aircraft with carbon fiber composite materials has reached.70%, Civil Boeing787and AirbusA380Carbon fiber composites have accounted for their structural materials.50%Above, the amount of carbon fiber used per aircraft is up23Tons. Speaking of which, it seems a bit off topic. However, in the last century60In the 1990 s, when the study began to turn brittle carbon materials into flexible carbon fibers, who would have thought of such a development today. From the development of carbon fibers, we can not see graphene tomorrow?

As“Previous”For another metaphor mentioned in, see“Science”A paper in the magazine ( Science ,18 July 2008.Vol. 321. no. 5887, pp. 385 - 388, “Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene ). The author is a physicist at Columbia University.Changgu Lee, James HoneThey have conducted a comprehensive study of the mechanical properties of graphene. To this end, they select some10-20As the research object, these graphene samples are first placed on a crystal sheet with small holes drilled on the surface. The diameter of these holes is1-1.5Between microns. A probe made of diamond is then used to apply pressure to the graphene placed on the small hole to test their ability to withstand. It was found that before the graphene sample began to fragment, each of its100The maximum pressure that can be withstood at a distance of about2.9Micro cattle. It is calculated that this result is equivalent to imposing55Newton's pressure can make1Meters of graphene fracture. If the thickness is equivalent to that of ordinary food plastic packaging bags (thickness is about100Nano) graphene, then it needs to apply almost 20,000 newtons of pressure to tear it off. In other words, if the packaging bag is made of graphene, it will be able to withstand about two tons of objects.

NatureandScienceIt is recognized as the world's top scientific journal. The papers and data published on it, I am afraid that not many people will think that the author of the paper is deceiving people?

As“Previous”Last mentioned, graphene as a material application of its research road is still very long. At present, it is not manufactured at all.1Meters of graphene, non-scientific and technical personnel may not be able to see, also can not touch it. When a large area of graphene is produced, its performance may also change.

Space elevator renderings

Space Elevator Concept

Although the existence of graphene has long been known, the successful separation of single-layer graphene is only6In, its understanding and research and development have just begun, and carbon fiber carbon nanotubes, as long as the direction of continuous efforts, good wishes and practical prospects may be realized. What's more, in today's world, both physicists, chemists and materials scientists are rushing to study graphene, a new material. That's why JapanITThe company and NASA (NASA) and other institutions, based on the high strength and light weight of carbon nanotubes and graphene, have proposed to use carbon nanotubes or graphene as cables to develop a ladder to space. Such a bold idea, in the eyes of some short-sighted people, is not more considered to be a fool?

This article is from Wang Maozhang Science Net blog.

Link address: http://blog.sciencenet.cn/home.php?mod=space&uid=526286