Carbon Nanotubes: A "Maverick" Magical Material
From:First Element   Date:2020-02-28   Hits:345

Do you know what is the most "black" material in the world? Recently, researchers from a foreign college have used carbon nanotubes to create a material that can absorb more than 99.96% of incident light, which can be called a "black hole" in the material family. Coincidentally, the same is the carbon nanotube material. Researchers use more than 14,000 carbon nanotube transistors to create 16-bit microprocessor chips and send a "Hello, World" message to the world.

Carbon nanotubes, as a one-dimensional quantum material with a special structure, possess many extraordinary mechanical, electrical, thermal and other physical and chemical properties. Please see--

"The King of Materials" with excellent performance

Before carbon nanotubes appeared in front of the world, silicon was the well-deserved "king*" in the semiconductor family. The core of every existing transistor is a semiconductor component made of silicon. According to the "on" and "off" states of the transistor, it shows whether there is current passing through, and then the "computer language" of 1 and 0 is displayed in the computer. However, silicon transistors are gradually facing development bottlenecks in terms of volume and performance, so people are focusing more on emerging materials such as carbon nanotubes.

Carbon nanotubes, also known as bucky tubes, are coaxial round tubes with several or dozens of layers composed of carbon atoms arranged in a hexagonal shape. The diameter of the tube is generally 2 to 20 nanometers. Compared with hair strands, the diameter of carbon nanotubes is only one tens of thousands of its diameter, and the diameter of the thinnest carbon nanotubes currently publicly reported is 0.4 nanometers. It is precisely because carbon nanotubes are almost as thick as atoms and can transmit current well, people can use carbon nanotubes to make semiconductors that are better than silicon.

Studies have shown that the running speed of carbon nanotube processors is twice as fast as silicon processors, but the power consumption is only 1/3 of that of silicon processors. A new generation of electronic products with excellent performance is about to emerge.

In fact, carbon nanotubes also have many magical properties that can be called "mavericks". As a material with better mechanical properties discovered so far, carbon nanotubes have extremely high tensile strength, Young's modulus and fracture strain. Compared with the high-strength steel of ASTMA228, the strength of carbon nanotubes is 270 times that of it, the elasticity is about 5 times that of it, but the density is only 1/6 of it.

In addition, carbon nanotubes also have excellent performance beyond traditional electrical and thermal conductivity materials in terms of electricity, heat, and optics. Theoretically speaking, the conductivity of carbon nanotubes is 10 times that of silicon. Once carbon nanotubes are widely used, "Silicon Valley" may really be a misnomer.

"Taming" carbon nanotubes is particularly difficult

As early as 1985, as soon as the fullerene of the "football" structure was discovered, it immediately attracted the attention of the world. Based on the "football" structure, with a little modification, a carbon nanotube with a hollow cylindrical structure can be formed. In 1991, Japanese researchers discovered carbon nanotubes in carbon fibers for the first time. Subsequently, the researchers discovered the excellent electrical conductivity of carbon nanotubes and many other properties. At present, people are working towards batch production of single carbon nanotubes with a length of meters or even kilometers.

It is not easy to "tame" carbon nanotubes, the "king of materials". Although carbon nanotubes are a kind of semiconductor, the current manufacturing process requires the use of metal, and metal impurities will inevitably be mixed into the finished material. At the same time, to convert carbon nanotubes into electronic components, the nanotubes need to be placed in extremely precise positions. At present, people have not yet mastered the method to make carbon nanotubes grow in specific locations. Carbon nanotubes also put forward extremely high requirements on the "birth room" of their "born": once the ambient temperature is too high and the catalyst loses activity, the carbon nanotubes will stop "growth"; on the contrary, if the control is slightly poor, the carbon nanotubes The tube will "grow crazily" again.

In fact, as early as 2013, relevant researchers produced the first carbon nanotube computer with 178 transistors, each of which contained carbon nanotubes about 10 to 200 nanometers long. Today, carbon nanotube computer transistors with a diameter of about 1 micron have been successfully developed, which can switch about 1 million times per second. In addition, the researchers also found that carbon nanotubes have excellent hydrogen storage properties and are expected to become materials for hydrogen energy batteries, which can be widely used in electric vehicles, submarines, electric locomotives and other fields.

People also plan to twist tens of thousands of carbon nanotubes together to form a macroscopic fiber. This type of carbon nanotube fiber, called the "final fiber", will have great strategic significance for the development of high-end technology in the 21st century. Once people make a breakthrough in the field of "taming" carbon nanotubes, a technological revolution initiated by carbon nanotubes will "detonate" the world.

Application prospects may change the world

Build a "space ladder" between the earth and the moon or a space base. This scene has appeared in many science fiction novels including "Three-Body". If you want to build a lunar-ground "space ladder", you must find a material that can span a distance of 380,000 kilometers without being pulled off by its own weight. As one of the materials with better mechanical properties discovered so far, carbon nanotubes have extremely high tensile strength, which may help people "climb into space" from the earth. In the future, human beings may be able to come and go as freely as taking an elevator when they enter space or transport materials into the space station.

Also with the help of the unique mechanical properties of carbon nanotubes, researchers are trying to study the manufacture of "black technology" products such as "constantly pulled" rope, "unbreakable" fiber cloth, and "impermeable" body armor. The blades used in wind turbines require extremely high material strength and rigidity. Reinforced composite materials made of carbon nanotube fibers will become a better choice. Carbon nanotube fiber-reinforced composite materials also have excellent fatigue resistance. When used in bridges and buildings, they can not only improve strength and earthquake resistance, but also extend their service life. In the future, including golf clubs, fishing rods, tennis rackets, bicycles, automobiles, high-speed trains, etc., carbon nanotube materials can be used.

Storing energy in carbon nanotubes, equipment similar to "Iron Man" will also become a reality. At present, a foreign laboratory is leading the development of a new type of clothing that can provide electricity to the outside world. This kind of clothing that turns carbon nanotubes into textile fabrics will provide electricity for lighting devices, night vision devices, and communication equipment used on the battlefield, which is bound to further reduce the burden on individual soldiers.

In addition, some researchers have also developed a sensor fabric that can sensitively know pressure changes by synthesizing carbon nanotube materials, which can play an important role in the field of sports training. People have also tried to make carbon nanotubes into a transparent conductive film as an alternative material for touch screens.

There are many future applications of carbon nanotubes. Due to the special structure and dielectric properties, carbon nanotubes exhibit strong broadband microwave absorption performance, and are an ideal microwave absorber with a bright future. They can be used as stealth materials, electromagnetic shielding materials or anechoic chamber absorbing materials. At the same time, the researchers imaginatively make carbon nanotubes into microchips that can be injected into the human body. They also plan to turn carbon nanotubes into nanorobots that can kill cancer cells in the human body.

The picture shows a schematic diagram of the structure of carbon nanotubes.

Photo courtesy: Liu Cheng
Source: China Military Network