3. Waterproofing materials In construction, housing and communal services, various waterproofing materials are widely used, which are designed to protect building structures, buildings and structures from the harmful effects of water and chemically aggressive liquids -

4. Electrical insulating materials In the context of the widespread use of various electrical installations in almost all sectors of industry and the economy of the country as a whole, electrical insulating materials have become widely used. The most important characteristic

5. Lubricants In accordance with the standard, lubricants are classified by origin, physical condition, the presence of additives, purpose, and temperature of use. Lubricants are divided by origin or starting raw material

Materials It is impossible to determine exactly which materials are primary and which are secondary. Everything is important here. Incorrect selection of tiles can affect the aesthetic side, and incorrect selection of the adhesive layer (underlying layer) can affect

10.4.1. SOFT MAGNETIC MATERIALS For many years, structural low-carbon steel St10 with a carbon content of 0.1% was used for massive magnetic cores. The requirements for increasing magnetic induction and decreasing coercive force led to the development

10.4.3. FERRIMAGNETIC MATERIALS Currently, much attention is paid to ferrites. Ferrites trace their origins to magnetite, a naturally occurring permanent magnet known throughout human history. Natural mineral - iron ferrite, or

10.4.4. HARD MAGNETIC MATERIALS Until 1910, permanent magnets were made of carbon steel, since this steel has a relatively small coercive force Hc and a large induction Br, the ratio of the length of the magnets to the cross section was large.

Required materials The raw materials for cement tiles are Portland cement and quartz sand. To give cement tiles a smooth surface, they are usually coated with a layer of acrylic or acrylic-silicate paint. The protective paint layer provides it with high

Superhard materials (STM) - these include diamonds (natural and synthetic) and composite materials based on cubic boron nitride.

Diamond- one of the modifications of carbon. Due to the cubic structure of the crystal lattice, diamond is the hardest mineral known in nature. Its hardness is 5 times higher than that of a hard alloy, but the strength is low and natural diamond single crystals break into small fragments when critical loads are reached. Therefore, natural diamonds are used only in finishing operations, which are characterized by low power loads.

The heat resistance of diamonds is 700...800 °C (diamond burns at higher temperatures). Natural diamonds have high thermal conductivity and the lowest coefficient of friction.

Natural diamond is designated by the letter A , synthetic - AC . Natural diamonds are individual single crystals and their fragments, or intergrown crystals and aggregates. Synthetic diamonds are obtained in the form of fine-grained powders and are used to make abrasive wheels, pastes and micropowders. A separate group consists of polycrystalline diamonds (PDA) of the ASB (Ballas) and ASPK (Carbonado) brands. PCD, due to its polycrystalline structure, resists impact loads much better than diamond single crystals, and, despite its lower hardness compared to natural diamond, has higher tensile and transverse shear strengths. The impact strength of diamond polycrystals depends on the size of the diamond grains and decreases with their increase.

Diamond has a chemical affinity with nickel- and iron-containing materials, therefore, when cutting iron-based steels, intense adhesion of the material being processed occurs on the contact surfaces of the diamond tool. The carbon that makes up diamond reacts actively with these materials when heated. This leads to intensive wear of the diamond tool and limits the scope of its application, therefore natural diamonds are used mainly for fine turning of non-ferrous metals and alloys that do not contain carbon and iron. The most effective use of diamond tools is in finishing and finishing operations when processing parts made of non-ferrous metals and their alloys, as well as from various polymer composite materials. The tool can be used for turning discontinuous surfaces and for milling, but its durability will be shorter than when machining without impact.

In many cases, the greater wear resistance of cutters made from synthetic diamonds, observed in practice, compared to cutters made from natural diamonds, is explained by the difference in their structures. In natural diamond, cracks appear on the cutting edge, develop and can reach significant sizes. In PCD (synthetic diamond), the resulting cracks are stopped by the boundaries of the crystals, which determines their higher, 1.5...2.5 times, wear resistance.

Another promising area of ​​application for PCD is the processing of materials that are difficult to cut and cause rapid tool wear, such as particle boards, medium-density boards with a high adhesive content, coated with melamine resin, decorative laminate paper, as well as other materials. having an abrasive effect. Tools with PCD have a durability when processing such materials that is 200..300 times higher than the durability of carbide tools.

PCD tools in the form of replaceable polyhedral inserts have been successfully used in the processing of polymer composite materials. Their use makes it possible to increase durability by 15...20 times compared to tools made of hard alloy.

Cubic boron nitride(KNB, BN ) does not occur in nature; it is obtained artificially from “white graphite” at high pressures and temperatures in the presence of catalysts. In this case, the hexagonal lattice of graphite turns into a cubic lattice, similar to the lattice of diamond. Each boron atom is connected to four nitrogen atoms. In terms of hardness, CBN is somewhat inferior to diamond, but has higher heat resistance, reaching 1300...1500 °C, and it is practically inert to carbon and iron. Like diamond, CBN has increased brittleness and low bending strength.

There are several brands of CBN, grouped under the “composites” group. Varieties of CBN differ from each other in size, structure and properties of grains, percentage composition of the binder, as well as sintering technology.

The most widely used composites are: composite 01 (elbor-R), composite 05, composite 10 (hexanite-R) and composite 10D (two-layer plates with a working layer of hexanite R). Of these, the strongest is composite 10 ( σ and = 1000...1500 MPa), therefore it is used for shock loads. Other composites are used for impactless finishing of hardened steels, high-strength cast irons and some difficult-to-cut alloys. In many cases, turning with composites is more effective than the grinding process, since, due to its high thermal conductivity, CBN does not cause burns when working at high cutting speeds and at the same time provides low surface roughness.

Composites are used in the form of small plates of square, triangular and round shapes, fixed to the tool body by soldering or mechanically. Recently, hard alloy plates with a layer of composite or polycrystalline diamond deposited on them have also been used. Such multilayer plates have greater strength, wear resistance and are more convenient for fastening. They allow you to remove allowances of great depth.

The main reserve for increasing processing productivity for tools based on BN is the cutting speed (Table 11.), which can exceed the cutting speed of a carbide tool by 5 or more times.

Table 11. Cutting speeds allowed by various tool materials

The table shows that the greatest efficiency of using tools based on BN occurs when processing high-hard cast irons, steels and alloys.

One of the possibilities for increasing the efficiency of a tool based on BN is the use of cutting fluids (coolants), which for tools made of BN it is most effective to use them by spraying them at cutting speeds up to 90...100 m/min.

Another effective area for using tools equipped with polycrystalline composites is the processing of surfacing, which is used to strengthen parts of metallurgical production. Welded materials of very high hardness (up to HRC 60..62) are produced by electric arc or plasma surfacing with flux-cored wires or tapes.

The areas of application for cutting speed and feed of all groups of considered tool materials are approximately shown in Fig. 38.

Fig.38. Scope of application of various tool materials according to cutting speed V and submission s .

1 – high-speed steels; 2 – hard alloys; 3 – hard alloys with coatings; 4 – nitride ceramics; 5 – oxide-carbide (black) ceramics; 6 - oxide ceramics; 7 – cubic boron nitride.

One of the directions for improving the cutting properties of tools, which makes it possible to increase labor productivity during machining, is to increase the hardness and heat resistance of tool materials. The most promising in this regard are diamond and synthetic superhard materials based on boron nitride.

Diamonds and diamond tools widely used in processing parts made of various materials. Diamonds are characterized by exceptionally high hardness and wear resistance. In terms of absolute hardness, diamond is 4-5 times harder than hard alloys and tens and hundreds of times higher than the wear resistance of other tool materials when processing non-ferrous alloys and plastics. In addition, due to their high thermal conductivity, diamonds better remove heat from the cutting zone, which helps ensure the production of parts with a burn-free surface. However, diamonds are very fragile, which greatly limits their scope of application.

The main application for the manufacture of cutting tools is artificial diamonds, which in their properties are close to natural. At high pressures and temperatures in artificial diamonds it is possible to obtain the same arrangement of carbon atoms as in natural ones. The weight of one artificial diamond is usually 1/8-1/10 carats (1 carat - 0.2 g). Due to the small size of artificial crystals, they are unsuitable for the manufacture of tools such as drills, cutters and others, and therefore are used in the manufacture of powders for diamond grinding wheels and lapping pastes.

Blade Diamond Tools are produced on the basis of polycrystalline materials such as “carbonado” or “ballas”. These tools have long dimensional tool life and provide high quality surface finishes. They are used in the processing of titanium, high-silicon aluminum alloys, fiberglass and plastics, hard alloys and other materials.

Diamond as a tool material has a significant drawback - at elevated temperatures it enters into a chemical reaction with iron and loses its functionality.

In order to process steel, cast iron and other iron-based materials, superhard materials, chemically inert to it. Such materials are obtained using a technology close to the technology for producing diamonds, but boron nitride, rather than graphite, is used as the starting material.

Polycrystals of dense modifications of boron nitride are superior in heat resistance to all materials used for blade tools: diamond by 1.9 times, high-speed steel by 2.3 times, hard alloy by 1.7 times, mineral ceramics by 1.2 times.

These materials are isotropic (the same strength in different directions), have a microhardness lower but close to the hardness of diamond, increased heat resistance, high thermal conductivity and chemical inertness with respect to carbon and iron.

The characteristics of some of the materials under consideration, which are currently called “composite,” are given in the table.

Comparative characteristics of STM based on boron nitride

The effectiveness of using blade tools made from various grades of composites is associated with improving the design of tools and their manufacturing technology and determining the rational area of ​​their use:

composites 01 (elbor-R) and 02 (belbor) used for fine and fine turning and impact-free milling of parts made of hardened steels with a hardness of 55...70 HRC, cast irons and hard alloys VK15, VK20 and VK25 with feeds up to 0.20 mm/rev and depth of cut up to 0.8

composite 05 used for finishing and semi-finish turning without impact of parts made of hardened steel with hardness 40...58 HRC, cast iron with hardness up to 300 HB with feeds up to 0.25 mm/rev and depth up to 2.5 mm

composite 10 (hexanite-R) used for fine, fine and semi-finish turning and milling with impacts of parts made of hardened steel with a hardness of no higher than 58 HRC, cast iron of any hardness, alloys VK15, VK20, VK25 with a feed of up to 0.15 mm/rev and a cutting depth of up to 0.6 mm

At the same time, the service life of tools increases tens of times compared to other tool materials.

In mechanical engineering, natural and synthetic minerals are widely used for the manufacture of cutting and abrasive tools. The most widely used natural minerals are diamond, quartz, and corundum; the most widely used synthetic minerals are diamonds, cubic boron nitride, electrocorundum, boron carbide, and silicon carbide. In many respects, synthetic materials are superior to natural ones. The main properties of synthetic superhard materials (SHM) used in cutting are given in Table 2.18.

Table 2.18

Basic properties of synthetic superhard materials

Natural and synthetic diamonds and cubic boron nitride CBN are used for blade processing. For abrasive - natural and synthetic diamonds, cubic boron nitride, corundum and electrocorundum, silicon carbide, boron carbide, aluminum oxide, chromium oxide, iron oxide, as well as some rocks.

Diamond is one of the natural superhard natural materials. The name “diamond” comes from the Arabic al-mas, which translates as “the hardest,” or the Greek adamas, which means “insurmountable, indestructible, invincible.” At the end of the 18th century. It was found that diamond is made of carbon. Diamonds are found in the form of individual well-defined crystals or in the form of a cluster of crystal grains and numerous intergrown crystals (aggregates). The unit of measurement for the size of a diamond is the carat (from Arab, kirat), which is 0.2 g.

It should be noted that natural diamonds are used very rarely in metalworking. As a rule, for these purposes they use bort (thrown overboard) - this is the name for all diamonds that are not used for making jewelry. Diamond crystals weighing 0.2-0.6 carats are used to make cutting tools (cutters, drills). Diamond powders are used to make diamond wheels. The diamond crystals are secured in the holder by silver soldering or mechanical fastening.

When sharpening, the diamond is first removed from the rod and ground in a technological holder on special machines using cast iron discs coated with a mixture of diamond powder and olive oil.

Polycrystals of synthetic diamonds are produced as ballas according to TU 2-037-19-70 (ASBZ and ASB4 for the manufacture of smoothers and ASPK2 for cutters). They are polycrystalline formations up to 12 mm in size, tightly bound crystals with high strength and wear resistance.

Areas of application of private labels:

• for diamonds (A) - processing of non-ferrous metals and their alloys, as well as wood, abrasive materials, plastics, hard alloys, glass, ceramics;
• for CBN - processing of ferrous metals, raw and hardened, as well as special alloys based on nickel and cobalt.

Currently, the industry mainly uses synthetic A, obtained from carbon (in the form of graphite) under high pressure and temperature, while the hexagonal face-centered lattice of graphite is transformed into a cubic face-centered diamond lattice. The temperature and pressure required for structural transformations are determined from the graphite-diamond phase diagram.

Since boron and nitrogen are located on both sides of carbon in the periodic table, through an appropriate chemical reaction it is possible to obtain a compound of these elements, i.e., boron nitride, which has a graphite-like hexagonal crystal lattice with approximately the same number of boron and nitrogen atoms arranged alternately. Similar to graphite, hexagonal boron nitride (HBN) has a layered, loose structure and can be transformed into CBN. This process is described by the state diagram of GNB - CBN. By adding special solvent catalysts (usually metal nitrides), the intensity of the transformation increases, and the pressure and temperature of the process are reduced, respectively, to 6 GPa and 1500°C. During the transformation, CBN crystals increase. When heated, individual CBN crystals are sintered together in the contact zones and form a “polycrystalline” mass. Solvents are also added to intensify sintering. In addition, the entire sintered mass must be at a certain pressure and temperature to prevent the reverse transformation of hard CBN crystals into soft hexagonal crystals.

As a result of sintering, a CBN conglomerate is obtained, in which randomly oriented anisotropic crystals are connected to each other, forming an isotropic mass of large volume. Then, from this mass, plates for cutting tools, dies for wire drawing, tools for dressing grinding wheels, wear-resistant parts, etc. are obtained.

As a cutting material, diamond has high durability and a low coefficient of friction when paired with metal, which ensures high surface quality. Diamonds are used (natural and synthetic) for precision turning and boring of parts made of non-ferrous alloys. Diamonds are not used for processing carbon-containing metals (cast iron, steel), since due to the chemical affinity of the processed and tool materials, intensive wear of diamond cutters and carburization of the surface layer of the workpiece occurs.

Materials based on boron nitride are a crystalline cubic (CBN) or wurtzite-like (WNL) modification of a boron-nitrogen compound, synthesized using a technology similar to the production of synthetic diamonds. By varying technological factors, several different materials are obtained on this basis - CBN, cubonite, hexanite, etc. Polycrystals based on boron nitride are obtained up to 12 mm in size, they are used for processing steels and iron-based alloys.

In domestic production, materials based on boron nitride for abrasive tools are produced under the brand name elbor, and for blade tools - composite.

The emergence of each qualitatively new group of tool materials is characterized, first of all, by a significant, abrupt increase in cutting speeds and is therefore always accompanied by profound changes in machine tool construction and machining technology.

Cutting speed is the most important factor in intensifying the processing of materials by cutting using tools made of synthetic superhard materials in conditions where the reserves for significantly increasing the cutting speeds of traditional tool materials are practically exhausted.

At the same time, as recent studies show, cutting speed is also a very effective factor in solving the problem of chip breaking - one of the most difficult problems in metalworking.

At high cutting speeds, the work is almost completely converted into heat and segmented chips are formed, in which the segments are separated by a fragile narrow bridge of heavily deformed metal; short, crushed chips are actually produced. Automation of material processing processes with chip removal and a further increase in cutting speeds are inseparable.

A sharp increase in cutting speed, all other things being equal, provides a corresponding increase in the minute feed of the tool, i.e., process productivity, as well as a decrease in cutting force, work hardening and roughness of the machined surface, i.e., accuracy and quality of processing. It has also been established that when the cutting speed increases within certain limits, the reliability of the STM tool increases; this is fundamentally important in relation to automated equipment.

As a rule, part of the available reserve for increasing the cutting speed when moving from a carbide tool to a tool made of STM is used to reduce the thickness of the cut layer. For example, when the cast iron milling speed is increased by 10 times, the minute feed can be increased not by 10, but by 4 times, with a corresponding decrease in feed per revolution of 2.5 times. This provides an additional significant reduction in cutting force and surface roughness.

Polycrystals SV, SVS, dismite, SVBN, and carbonite are currently produced from materials obtained by sintering diamond grains.

Polycrystals of the ASB brand have a spherical shape with a diameter of about 6-6.5 mm, a clearly defined radial structure. Ballas crystals form a block structure and have different sizes across the cross-section of the sample: smaller in the center than at the periphery. Their size is in the range of 10-300 microns.

Diamonds of the ASPC brand have the shape of a cylinder with a diameter of 2-4.5 mm, a height of 3-5 mm, their structure is also radial, but more finely formed and perfect. The grain sizes are smaller (up to 200 microns).

The structure of SV type diamonds is polycrystalline, two-phase. The total amount of impurities does not exceed 2%.

In order of increasing strength, diamond polycrystals are arranged as follows: ASB, ASPK, SV, dismite.

Diamond tools can be operated, unlike composite tools, at low speeds inherent in carbide tools, providing a manifold increase in durability. When milling, speeds can be increased by 1.5-2 times. The cutting depth of wood-based particle board materials is determined by the width of the cutters or saws.

The effectiveness of using CA in processing high-hard materials can be illustrated by the example of turning hard alloys VK10, VK10S, VS15, VK20 with ASPC cutters. The productivity of such processing is ten times higher than the productivity of grinding while consistently ensuring the specified quality.

High wear resistance is revealed by tools made of ASP and ASB when turning abrasive materials, widespread high-silicon and copper alloys, fiberglass, plastic ceramics, press materials, etc. It is ten or more times higher than that of carbide.

Considerable experience has been accumulated in turning and boring workpieces made of aluminum alloys AL-2, AL-9, AL-25, AK-6, AK-9, AK-12M2, VKZhLS-2, titanium alloys VT6, VT22, VT8, VTZ with ASPC cutters. -1, fiberglass, non-ferrous metals, wood.

ASB polycrystals are characterized by high performance when turning high-silicon aluminum alloy AK-21, AL-25, copper-based alloy L62, when processing LS59-1, bronze, fiberglass plastics ST, SVAM, AG, etc.

What materials are considered superhard? What is their range of application? Are there materials harder than diamond? Professor, PhD in Crystallography Artem Oganov talks about this.

Superhard materials are materials that have a hardness above 40 gigapascals. Hardness is a property that is traditionally measured by scratching. If one material scratches another, it is considered to have higher hardness. This is relative hardness; it does not have strict quantitative characteristics. Strict quantitative characteristics of hardness are determined using a pressure test. When you take a pyramid, usually made of diamond, apply some force and press the pyramid onto the surface of your test material, measure the pressure, measure the area of ​​the indentation, apply a correction factor, and this value will be the hardness of your material. It has the dimension of pressure because it is force divided by area, so gigapascals (GPa).

40 GPa is the hardness of cubic polycrystalline boron nitride. This is a classic super-hard material that is widely used. The hardest material known to mankind so far is diamond. For a long time there have been attempts, which continue even now, to discover a material harder than diamond. So far, these attempts have not led to success.

Why are superhard materials needed? The number of superhard materials is small, about ten, maybe fifteen materials known today. Firstly, superhard materials can be used for cutting, polishing, grinding, and drilling. For tasks related to machine tool building, jewelry making, stone processing, mining, drilling, and so on, all this requires super-hard materials.

Diamond is the hardest material, but it is not the most optimal material. The fact is that diamond, firstly, is fragile, and secondly, diamond burns in an oxygen atmosphere. Imagine a drill that heats up to a high temperature in an oxygen atmosphere. Diamond, being elemental carbon, will burn. And besides, a diamond cannot cut steel. Why? Because carbon reacts with iron to form iron carbide, meaning your diamond will simply dissolve in steel at a high enough temperature, and so you need to look for some other materials. In addition, diamond is, of course, quite expensive; even synthetic diamond is not a cheap enough material.

Moreover, superhard materials may still be useful in body armor and other protective military devices. In particular, a material such as boron carbide, which is also super-hard and quite light, is widely used. This is the range of application of superhard materials.

It is known that superhard materials are formed in substances with strong covalent bonds. Ionic bonding reduces hardness. The metal bond also reduces hardness. The bonds must be strong, directed, that is, covalent, and as short as possible. The density of the substance should also be as high as possible, density in the sense of the number of atoms per unit volume. And, if possible, the symmetry of the substance should also be very high, so that the substance is equally strong in this direction, and in this, and in this. Otherwise, the story will be the same as in graphite, where the bonds are very strong, but only in two directions, and in the third direction the bonds between the layers are extremely weak, as a result the substance is also soft.

Many institutes, many laboratories around the world are engaged in the synthesis and development of superhard materials. In particular, these are the Institute of High Pressure Physics in the Moscow region, the Institute of Superhard and New Carbon Materials in the Moscow region, the Institute of Superhard Materials in Kyiv and a number of laboratories in the West. Active developments in this area began, I think, in the 50s, when artificial diamonds were first produced in Sweden and America. At first, these developments were secret, but soon enough the synthesis of artificial diamonds was also established in the Soviet Union, precisely thanks to the work of researchers from the Institute of High Pressure Physics and the Institute of Superhard Materials.

There have been various attempts to create materials harder than diamond. The first attempt was based on fullerenes. - these are molecules similar to a soccer ball, hollow molecules, round or somewhat elongated. The bonds between these molecules are very weak. That is, it is a molecular crystal consisting of healthy molecules. But the bonds between the molecules are weak, van der Waals. If this kind of crystal is squeezed, then bonds will begin to form between the molecules, between these balls, and the structure will turn into a three-dimensionally connected covalent very hard structure. This material was named tisnumite in honor of the Technological Institute of Superhard and New Carbon Materials. It was assumed that this material was harder than diamond, but further research showed that this was most likely not the case.

There have been proposals and quite active discussion that carbon nitrides could be harder than diamond, but despite active discussion and active research, such a material has not yet been presented to the world.

There was a rather funny work by Chinese researchers, in which they suggested, based on theoretical calculations, that another modification of carbon is similar to diamond in many ways, but is slightly different from it, and is called lonsdaleite. According to this work, lonsdaleite is harder than diamond. Lonsdaleite is an interesting material; thin lamellae of this material have been found in shock-compressed diamond. This mineral was named after the famous woman Kathleen Lonsdale, a great British crystallographer who lived in the 50s–70s of the 20th century. She had an extremely interesting biography; she even spent time in prison when she refused to put out fires during World War II. She was a Quaker by religion, and Quakers were prohibited from any activities related to war, even putting out fires. And for this they put her in a paddy wagon. But nevertheless, everything was fine with her, she was the president of the International Union of Crystallography, and this mineral was named in her honor.

Lonsdaleite, judging by all available experimental and theoretical data, is still softer than diamond. If you look at the work of these Chinese researchers, you can see that even according to their calculations, lonsdaleite is softer than diamond. But somehow the conclusion was drawn contrary to their own results.

Thus, it turns out that there is no real candidate to displace diamond as the hardest substance. But nevertheless, the issue is worth exploring. Still, many laboratories are still trying to create such a material. Using our method for predicting crystal structures, we decided to ask this question. And the problem can be formulated as follows: you are not looking for a substance that has maximum stability, but a substance that has maximum hardness. You give a range of chemical compositions, for example from pure carbon to pure nitrogen, and everything in between, all possible carbon nitrides, are included in your calculation, and evolutionarily try to find harder and harder compositions and structures.

The hardest substance in this system is the same diamond, and adding nitrogen to carbon does not improve anything in this system.

Thus, the hypothesis of carbon nitrides as substances harder than diamond can be buried.

We tried everything else that was suggested in the literature, different forms of carbon and so on - in all cases, diamond always won. So it looks like the diamond cannot be removed from this pedestal. But it is possible to invent new materials that are preferable to diamond in a number of other respects, for example, in the sense of crack resistance or in terms of chemical resistance.

For example, elemental boron. We discovered the structure, a new modification of boron. We published this article in 2009, and it caused a tremendous response. The structure is obtained by applying slight pressure to ordinary boron and heating it to high temperatures. We called this form gamma-boron, and it turned out that it contains a partial ionic chemical bond. In fact, this is something that will slightly reduce the hardness, but due to its high density, this modification still turns out to be the hardest known modification of boron, its hardness is about 50 GPa. The pressures for synthesis are small, and therefore, in principle, one can even think about its synthesis in fairly large volumes.

We have predicted a number of other superhard phases, such as phases in the tungsten-boron system, chromium-boron, and so on. All of these phases are superhard, but their hardnesses are still at the lower end of this range. They are closer to the 40 GPa mark than to the 90–100 GPa mark, which corresponds to the hardness of diamond.

But the search continues, we do not despair, and it is quite possible that we or our other colleagues working on this topic around the world will be able to invent a material that can be synthesized at low pressures and that will be close to diamond in hardness. We and other colleagues have already done something in this area. But how to apply this technologically is not yet entirely clear.

I'll tell you about a new form of carbon, which was actually produced experimentally back in 1963 by American researchers. The experiment was conceptually quite simple: they took carbon in the form of graphite and compressed it at room temperature. The fact is that you can’t get a diamond this way; a diamond requires strong heating. Instead of diamond, a transparent superhard non-metallic phase was formed in their experiments, but nevertheless it was not diamond. And this was in no way consistent with the characteristics of any of the known forms of carbon. What's the matter, what kind of structure is this?

Quite by accident, while studying various carbon structures, we came across one structure that was only slightly inferior to diamond in stability. Only three years after we saw this structure, looked at it, even published it somewhere between the lines, it dawned on us that it would be nice to compare the properties of this structure with what has been published by all those researchers since 1963 and right up to very recent years. And it turned out that there is a complete coincidence. We were happy, we quickly published an article in one of the most prestigious magazines, The Physical Review Letters, and a year later an article in the same journal was published by American and Japanese researchers who discovered that a completely different structure of carbon also described the same experimental data. The problem is that the experimental data were of rather poor resolution. So who is right?

Soon, Swiss and Chinese researchers proposed a number of modifications. And towards the end, one Chinese researcher published about forty carbon structures, most of which also describe the same experimental data. He promised me that if he was not too lazy, he would offer about a hundred more structures. So what is the right structure?

To do this, we had to study the kinetics of the transformation of graphite into various carbon structures, and it turned out that we were very lucky. It turned out that our structure is the most preferable from the point of view of transformation kinetics.

A month after the publication of our article, an experimental work was published in which the experimenters did the most accurate experiment with data of much better resolution than before, and it really turned out that out of all those dozens of published structures, only one structure explains the experimental data - it is still our structure. We called this new material M-carbon because its symmetry is monoclinic, from the first letter M.

This material is only slightly inferior in hardness to diamond, but whether there is any property in which it is superior to diamond is still unclear.

Until now it is, one might say, a “thing in itself.” We continue our search and hope that we will be able to invent a material that, while not much inferior to diamond in hardness, will significantly surpass it in all other characteristics.

One of the ways to improve the mechanical characteristics of substances is to nanostructure them. In particular, the hardness of the same diamond can be increased by creating diamond nanocomposites or diamond nanopolycrystals. In such cases, the hardness can be increased even by 2 times. And this was done by Japanese researchers, and now you can see the products that they produce, quite large, on the order of a cubic centimeter, diamond nanopolycrystals. The main problem with these nanopolycrystals is that they are so hard that it is almost impossible to even polish them, and it takes a whole laboratory to polish it for weeks.

In this way, you can both change the chemistry, change the structure of a substance in search of improving its hardness and other characteristics, and change the dimension.