Carbon nanotubes: production, applications, properties

Energy is an important industry, which plays a huge role in human life. The energy situation in the country depends on the work of many scientists in the industry. To date, they are looking for alternative sources of energy. For this purpose, they are ready to use anything they like, starting with sunlight and water, ending with the energy of the air. That equipment that is capable of generating energy from the environment is very much appreciated.

General information

Carbon nanotubes are long drawn flat graphitic planes that have a cylindrical shape. As a rule, their thickness reaches several tens of nanometers, with a length of several centimeters. At the end of the nanotubes a spherical head is formed, which is one of the parts of the fullerene.

There are such types of carbon nanotubes: metal and semiconductor. Their main difference is the conductivity of the current. The first type can conduct current at a temperature of 0 ° C, and the second - only at elevated temperatures.

Carbon nanotubes: properties

Most modern trends, such as applied chemistry or nanotechnology, are associated with nanotubes that have a carbon framework. What it is? Under this structure is meant large molecules that are linked only by carbon atoms. Carbon nanotubes, whose properties are based on the closed form of the shell, are very much appreciated. In addition, the formation data have a cylindrical shape. Such tubes can be obtained by folding the graphite sheet, or growing from a certain catalyst. Carbon nanotubes, the photos of which are presented below, have an unusual structure. They come in different shapes and sizes: single-layered and multi-layered, straight and sinuous. Despite the fact that the nanotubes look rather brittle, they are a durable material. As a result of many studies, it was found that they have inherent properties such as stretching and bending. Under the action of serious mechanical loads, the elements do not tear and do not break, that is, they can be adjusted for different stresses.

Toxicity

As a result of multiple studies, it was found that carbon nanotubes can cause the same problems as asbestos fibers, that is, there are various malignant tumors, as well as lung cancer. The degree of negative influence of asbestos depends on the type and thickness of its fibers. Since carbon nanotubes have a small weight and dimensions, they easily enter the human body together with air. Further, they enter the pleura and enter the thorax, and in time cause various complications. Scientists conducted an experiment, and added to the food of mice particles of nanotubes. Products of small diameter were practically not retained in the body, but larger ones were digging into the walls of the stomach and causing various diseases.

Methods of obtaining

To date, there are the following methods for obtaining carbon nanotubes: arc charge, ablation, deposition from the gas phase.

Electric arc discharge. The preparation (carbon nanotubes are described in this paper) in an electric charge plasma that burns with the use of helium. Such a process can be carried out with the help of special technical equipment for obtaining fullerenes. But this method uses other modes of arc burning. For example, the current density is lowered, and cathodes of enormous thickness are also used. To create an atmosphere of helium, it is necessary to increase the pressure of this chemical element. Carbon nanotubes are obtained by spraying. In order to increase their number, it is necessary to introduce a catalyst into the graphite rod. Most often it is a mixture of different metal groups. Further, the pressure and method of spraying change. Thus, a cathode deposit is obtained, where carbon nanotubes are formed. Finished products grow perpendicularly from the cathode and are assembled into bundles. They have a length of 40 μm.

Ablation. This method was invented by Richard Smalli. Its essence is to vaporize different graphite surfaces in a reactor operating at high temperatures. Carbon nanotubes are formed as a result of the evaporation of graphite on the lower part of the reactor. Cooling and collection of them occurs with the help of a cooling surface. If in the first case, the number of elements was 60%, then with this method the figure increased by 10%. The cost of the laser ablation method is more expensive than all the others. As a rule, single-walled nanotubes are produced due to a change in the reaction temperature.

Precipitation from the gas phase. The method of depositing carbon vapors was invented in the late 1950s. But no one even imagined that carbon nanotubes could be produced with the help of it. So, first you need to prepare a surface with a catalyst. As it can serve fine particles of different metals, for example, cobalt, nickel and many others. Nanotubes begin to emerge from the catalyst bed. Their thickness directly depends on the size of the catalyzing metal. The surface is heated to high temperatures, and then a gas containing carbon is supplied. Among them - methane, acetal, ethanol, etc. As an additional technical gas is ammonia. This method of obtaining nanotubes is the most common. The process itself takes place in various industrial enterprises, which means that less money is spent to produce a large number of tubes. Another advantage of this method is that vertical elements can be obtained from any metal particles serving as a catalyst. The production (carbon nanotubes are described from all sides) became possible thanks to the studies of Suomi Iijima, who observed under a microscope after their appearance as a result of carbon synthesis.

Basic views

Carbon elements are classified by the number of layers. The simplest form is single-walled carbon nanotubes. Each of them has a thickness of about 1 nm, and their length can be much larger. If we consider the structure, then the product looks like wrapping graphite with a hexagonal grid. At its vertices are carbon atoms. Thus, the tube has the shape of a cylinder, which has no seams. The upper part of the devices is closed with lids consisting of fullerene molecules.

The next type is multilayered carbon nanotubes. They consist of several layers of graphite, which are stacked in the shape of a cylinder. Between them, a distance of 0.34 nm is maintained. A structure of this type is described in two ways. On the first, multilayer tubes are several nested single-layered tubes that are similar to a nesting doll. In the second, multilayered nanotubes are a sheet of graphite, which turns around itself several times, which looks like a folded newspaper.

Carbon nanotubes: application

Elements are an absolute new representative of the class of nanomaterials. As mentioned before, they have a framework structure, which differs in properties from graphite or diamond. That's why they are used much more often than other materials.

Due to such characteristics as strength, bending, conductivity, are used in many areas:

• As additives to polymers;
• Catalyst for lighting devices, as well as flat displays and tubes in telecommunications networks;
• As an absorber of electromagnetic waves;
• For energy conversion;
• Manufacturing of anodes in different types of batteries;
• Storage of hydrogen;
• Manufacturing of sensors and capacitors;
• Production of composites and strengthening their structure and properties.

For many years, carbon nanotubes, the use of which is not limited to one particular industry, is used in scientific research. Such material has weak positions in the market, as there are problems with large-scale production. Another important point is the high cost of carbon nanotubes, which is about $ 120 per gram of such a substance.

They are used as the main element for the production of many composites, which are used to manufacture many sports products. Another industry is car manufacturing. The functionalization of carbon nanotubes in this field is reduced to imparting polymers to conductive properties.

The coefficient of thermal conductivity of nanotubes is high enough, therefore they can be used as a cooling device for various massive equipment. Also, of them, the tips are made, which are attached to the probe tubes.

The most important field of application are computer technologies. Thanks to nanotubes, especially flat displays are created. With their help, you can significantly reduce the overall dimensions of the computer itself, as well as increase its technical performance. Finished equipment will be several times superior to current technologies. Based on these studies, high-voltage kinescopes can be created.

Over time, the tubes will be used not only in electronics, but also in medical and energy fields.

Production

Carbon tubes, the production of which is distributed between their two species, is distributed unevenly. That is, MWNT produce much more than SWNT. The second kind is done in case of acute necessity. Different firms constantly produce carbon nanotubes. But they practically do not use demand, as their cost is overstated.

Production Leaders

To date, the leading place in the production of carbon nanotubes is occupied by the countries of Asia, whose production capacities are three times higher than in other countries of Europe and America. In particular, Japan is the manufacturer of MWNT. But other countries, such as Korea and China, are in no way inferior in this indicator.

Production in Russia

Domestic production of carbon nanotubes lags far behind other countries. In fact, everything depends on the quality of the research in this area. It does not allocate enough financial resources to create scientific and technological centers in the country. Many people do not perceive developments in the field of nanotechnology, because they do not know how it can be used in industry. Therefore, the transition of the economy to a new trail is rather difficult.

Therefore, the President of Russia issued a decree, which indicates the development of various areas of nanotechnology, including carbon elements. For these purposes, a special program for the development and production of own technologies was created. To ensure that all items of the order were executed, the company "Rosnanotech" was established. A significant amount from the state budget was allocated for its functioning. It is she who must control the process of development, production and introduction into the industrial sphere of carbon nanotubes. The allocated sum will be spent on creation of various research institutes and laboratories, and also will allow to strengthen already existing achievements of domestic scientists. Also, these funds will go to purchase high-quality equipment for the production of carbon nanotubes. It is also necessary to take care of those adaptations that will protect human health, since this material causes many diseases.

As stated earlier, the whole problem is attracting funds. Most investors do not want to invest in scientific developments, especially for a long time. All businessmen want to see profit, but nanoscale can go for years. It is this that repels representatives of small and medium-sized businesses. In addition, without public investment, it will not be possible to fully launch the production of nanomaterials. Another problem is the lack of a legal framework, since there is no intermediate link between the different levels of business. Therefore, carbon nanotubes, whose production in Russia is not in demand, require not only financial but also mental investments. While Russia is far from the countries of Asia, which are leading in the development of nanotechnology.

To date, developments in this field are being carried out at the chemical faculties of various universities in Moscow, Tambov, St. Petersburg, Novosibirsk and Kazan. Leading manufacturers of carbon nanotubes are the company "Granat" and Tambov plant "Komsomolets".

Positive and negative sides

Among the merits, one can single out the special properties of carbon nanotubes. They are a durable material that does not collapse under the influence of mechanical influences. In addition, they work well for bending and stretching. This was made possible by a closed frame structure. Their application is not limited to one industry. Tubes have found application in automotive, electronics, medicine and energy.

A huge disadvantage is the negative impact on human health. Particles of nanotubes, getting into the human body, lead to the appearance of malignant tumors and cancer.

The essential part is financing this industry. Many people do not want to invest in science, because it takes a lot of time to get profit. And without the functioning of scientific research laboratories, the development of nanotechnology is impossible.

Conclusion

Carbon nanotubes play an important role in innovative technologies. Many experts predict the growth of this industry in the coming years. There will be a significant increase in production opportunities, which will lead to a decrease in the cost of the goods. With the reduction in price, the tubes will be in great demand, and will become an indispensable material for many devices and equipment.

So, we found out what these products represent.