Application of crystals. Main applications of artificial crystals

Living on an Earth composed of crystalline rocks, we, of course, cannot escape from the problem of crystallinity: we walk on crystals, build with crystals, process crystals in factories, grow them in laboratories, widely use them in technology and science, eat crystals, and receive treatment. them... The science of crystallography studies the variety of crystals. She comprehensively examines crystalline substances, studies their properties and structure. In ancient times, crystals were considered to be rare. Indeed, the discovery of large homogeneous crystals in nature is a rare phenomenon. However, finely crystalline substances are quite common. For example, almost all rocks: granite, sandstone, limestone are crystalline. As research methods improved, substances that were previously considered amorphous turned out to be crystalline. Now we know that even some parts of the body are crystalline, for example, the cornea of the eye, vitamins, the melin sheath of the nerves are crystals. The long path of searches and discoveries, from measuring the external shape of crystals to the depths of their atomic structure, has not yet been completed. But now researchers have studied its structure quite well and are learning to control the properties of the crystals.

Crystals are beautiful, one might say some kind of miracle, they attract you; They say “a man of crystal soul” about someone who has a pure soul. Crystal means shining with light, like a diamond... And if we talk about crystals with a philosophical attitude, then we can say that this is a material that is an intermediate link between living and inanimate matter. Crystals can originate, age, and collapse. A crystal, when growing on a seed (on an embryo), inherits the defects of this very embryo. In general, one can give many examples that set one in such a philosophical mood, although of course there is a lot of evil here... For example, on television one can now hear about the direct connection between the degree of order of water molecules and words, with music, and that water changes depending on thoughts, on the health status of the observer. I don't take it seriously. In fact, there is a lot of quackery and speculation around science. But prayer is mediated, it acts through the Holy Spirit, and there is no need to mix the scientific approach and spiritual things.

But speaking quite seriously, now it is perhaps impossible to name a single discipline, not a single area of science and technology that could do without crystals. When I was working, doctors flocked to me and showed me patients’ kidney stones: they were interested in the environments in which crystal formation occurred. And we visited a lot of pharmacists, because tablets are compressed crystals. The absorption and dissolution of tablets depends on which edges these microcrystals are covered with. Vitamins, the myelin sheath of nerves, proteins, and viruses are all crystals. And our consultations brought great satisfaction, answering questions that arose...

The crystal has miraculous properties; it performs a variety of functions. These properties are inherent in its structure, which has a three-dimensional lattice structure.

An example of the use of crystals is the quartz crystal used in telephone handsets. If a quartz plate is mechanically affected, an electric charge will arise in it in the corresponding direction. In the microphone tube, quartz converts mechanical air vibrations caused by the speaker into electrical ones. Electrical vibrations in your subscriber's handset are converted into oscillatory vibrations, and, accordingly, he hears speech.

Being lattice, the crystal is faceted and each face, like a personality, is unique. If a face is densely packed in a lattice with material particles (atoms or molecules), then it is a very slowly growing face. For example, a diamond. Its faces have the shape of an octahedron, they are very densely packed with carbon atoms, and due to this they differ in both brilliance and strength.

Crystallography is not a new science. M.V. Lomonosov stands at its origins. But growing artificial crystals is a later matter. Shubnikov's popular book "The Formation of Crystals" was published in 1947. This scientific practice grew out of mineralogy, the science of crystals and amorphous solids. Growing crystals became possible thanks to the study of mineralogy data on crystal formation in natural conditions. By studying the nature of the crystals, they determined the composition from which they grew and the conditions for their growth. And now these processes are imitated, obtaining crystals with specified properties. Chemists and physicists take part in the production of crystals. If the former develop growth technology, the latter determine their properties. Can artificial crystals be distinguished from natural ones? Here's the question. Well, for example, artificial diamond is still inferior to natural diamond in quality, including in brilliance. Artificial diamonds do not evoke jewelry joy, but they are quite suitable for use in technology, and in this sense they are on an equal footing with natural ones. Again, impudent growers (the so-called chemists who grow artificial crystals) have learned to grow the finest crystal needles with extremely high strength. This is achieved by manipulating the chemistry of the medium, temperature, pressure, and exposure to some other additional conditions. And this is already a whole art, creativity, skill - the exact sciences will not help here, they work poorly in this area. The late academician Nikolai Vasilyevich Belov said that the art of growing a crystal belongs to the specialist who has a keen sense of the crystal.

Goals: show the role of mono- and polycrystals in technology and science, the variety of shapes of crystal lattices; consider various methods for growing single crystals and ways to increase their strength.

During the classes

1. Organizational stage (1 min)

2. Presentation of new material (43 min)

Solid state physics (a branch of physics that studies the structure and properties of solids) is one of the foundations of modern technological society. In essence, a huge army of engineers around the world is working to create solid materials with specified properties necessary for use in a wide variety of machines, mechanisms and devices in the field of communications, transport and computer technology. Today in the lesson we will talk about crystals. Our task: to find out how crystals are structured; explain from a physical point of view the diversity of their forms and properties; consider methods of artificially growing crystals and ways to increase their strength; see how and why crystals are used in everyday life and technology.

Crystalline substances are those whose atoms are arranged regularly so that they form a regular three-dimensional lattice called crystalline. Crystals of a number of chemical elements and their compounds have remarkable mechanical, electrical, magnetic and optical properties. ( Slideshow “Variety of Crystals”.)

The main difference between crystals and other solids is, as already mentioned, the presence of a crystal lattice - a collection of periodically arranged atoms, molecules or ions.

Student message. Russian scientist E.S. Fedorov found that only 230 different space groups can exist in nature, covering all possible crystal structures. Most of them (but not all) are found in nature or created artificially. Crystals can take the form of various prisms, the base of which can be a regular triangle, square, parallelogram and hexagon. ( Slide.)

Examples of simple crystal lattices: 1 – simple cubic; 2 – face-centered cubic; 3 – body-centered cubic; 4 – hexagonal

Crystal lattices of metals often have the form of a face-centered (copper, gold) or body-centered cube (iron), as well as a hexagonal prism (zinc, magnesium).

The classification of crystals and the explanation of their physical properties can be based not only on the shape of the unit cell, but also on other types of symmetry, for example, rotation around an axis. The axis of symmetry is a straight line, when rotated 360° around which the crystal aligns with itself several times. The number of these combinations is called axis order. There are crystal lattices with symmetry axes of 2nd, 3rd, 4th and 6th orders. Symmetry of the crystal lattice relative to the plane of symmetry is possible, as well as a combination of different types of symmetry. ( Slide.)

Most crystalline solids are polycrystals, because Under normal conditions, it is quite difficult to grow single crystals; all sorts of impurities interfere with this. In light of the growing need in technology for crystals of high purity, science is faced with the question of developing effective methods for artificially growing single crystals of various chemical elements and their compounds.

Student message. There are three ways to form crystals: crystallization from a melt, from a solution and from the gas phase. An example of crystallization from a melt is the formation of ice from water (after all, water is molten ice), as well as the formation of volcanic rocks. An example of crystallization from solution in nature is the precipitation of hundreds of millions of tons of salt from sea water. When a gas (or steam) cools, electrical forces of attraction force the atoms or molecules together into a crystalline solid—snowflakes are formed.

The most common methods for artificially growing single crystals are crystallization from solution and from a melt. In the first case, crystals grow from a saturated solution with slow evaporation of the solvent or with a slow decrease in temperature. This process can be demonstrated in the laboratory with an aqueous solution of table salt. If the water is allowed to evaporate slowly, the solution will eventually become saturated, and further evaporation will cause salt to precipitate.

If a solid substance is heated, it will turn into a liquid state - a melt. Difficulties in growing single crystals from melts are associated with high melting temperatures. For example, to obtain a ruby crystal, you need to melt aluminum oxide powder, and for this you need to heat it to a temperature of 2030 ° C. The powder is poured in a thin stream into an oxygen-hydrogen flame, where it melts and falls in drops onto a rod of refractory material. A single crystal of ruby gradually grows on this rod.

3. Application of crystals

1. Diamond. About 80% of all natural diamonds mined and all artificial diamonds are used in industry. Diamond tools are used for processing parts made of the hardest materials, for drilling wells during exploration and mining of mineral resources, and serve as supporting stones in high-class chronometers for marine vessels and other highly precise instruments. Diamond bearings show no wear even after 25 million revolutions. The high thermal conductivity of diamond allows it to be used as a heat-removing substrate in semiconductor electronic microcircuits.

Of course, diamonds are also used in jewelry - these are diamonds.

2. Ruby. The high hardness of rubies, or corundum, has led to their widespread use in industry. From 1 kg of synthetic ruby, about 40,000 watch support stones are obtained. Ruby thread guide rods turned out to be irreplaceable in chemical fiber factories. They practically do not wear out, while thread guides made of the hardest glass wear out in a few days when artificial fiber is pulled through them.

New prospects for the widespread use of rubies in scientific research and technology opened up with the invention of the ruby laser, in which a ruby rod serves as a powerful source of light emitted in the form of a thin beam.

3. . These are unusual substances that combine the properties of a crystalline solid and liquid. Like liquids they are fluid, like crystals they have anisotropy. The structure of liquid crystal molecules is such that the ends of the molecules interact very weakly with each other, while at the same time the side surfaces interact very strongly and can firmly hold the molecules in a single ensemble.

Liquid crystals: smectic (left) and cholesteric (right)

Cholesteric liquid crystals are of greatest interest to technology. In them, the direction of the molecular axes in each layer is slightly different from each other. The rotation angles of the axes depend on the temperature, and the color of the crystal depends on the rotation angle. This dependence is used in medicine: you can directly observe the temperature distribution over the surface of the human body, and this is important for identifying foci of the inflammatory process hidden under the skin. For research, a thin polymer film with microscopic cavities filled with cholesteric is produced. When such a film is applied to the body, a color display of the temperature distribution is obtained. The same principle is used in liquid crystal thermometers.

Liquid crystals are most widely used in alphanumeric indicators of electronic watches, microcalculators, etc. The desired number or letter is reproduced using a combination of small cells made in the form of stripes. Each cell is filled with liquid crystal and has two electrodes to which voltage is applied. Depending on the voltage, certain cells “light up”. Indicators can be made extremely miniature and consume little energy.

Liquid crystals are used in various types of controlled screens, optical shutters, and flat television screens.

4. Semiconductors. An exceptional role has been played by crystals in modern electronics. Many substances in the crystalline state are not as good conductors of electricity as metals, but they cannot be classified as dielectrics either, because They are not good insulators either. Such substances are classified as semiconductors. These are the majority of substances, their total mass is 4/5 of the mass of the earth’s crust: germanium, silicon, selenium, etc., many minerals, various oxides, sulfides, tellurides, etc.

The most characteristic property of semiconductors is the sharp dependence of their electrical resistivity under the influence of various external influences: temperature, lighting. The operation of devices such as thermistors and photoresistors is based on this phenomenon.

By combining semiconductors of different conductivity types, it is possible to pass electric current in only one direction. This property is widely used in diodes and transistors.

The exceptionally small size of semiconductor devices, sometimes only a few millimeters, durability due to the fact that their properties change little over time, and the ability to easily change their electrical conductivity open up broad prospects for the use of semiconductors today and in the future.

5. Semiconductors in microelectronics. An integrated circuit is a collection of a large number of interconnected components - transistors, diodes, resistors, capacitors, connecting wires, manufactured on one chip. When manufacturing an integrated circuit, layers of impurities, dielectrics, and layers of metal are deposited sequentially onto a semiconductor plate (usually silicon crystals). As a result, several thousand electrical microdevices are formed on one chip. The dimensions of such a microcircuit are usually 5–5 mm, and individual microdevices are about 10–6 m.

Recently, the possibility of creating electronic microcircuits in which the dimensions of the elements will be comparable to the dimensions of the molecules themselves, i.e., have increasingly begun to be discussed. about 10 –9 –10 –10 m. To do this, small amounts of atoms or molecules of other substances are sprayed onto the cleaned surface of a nickel or silicon single crystal using a tunnel microscope. The surface of the crystal is cooled to –269 °C to eliminate noticeable movements of atoms due to thermal motion. Placing individual atoms in specific locations opens up fantastic possibilities for creating atomic-level information stores. This is already the limit of “miniaturization”.

6. Tungsten and molybdenum. At the current level of technical development, the heating and cooling rates of instrument and machine parts have sharply increased, and the temperature range at which they have to operate has increased significantly. Very often long-term work is required at very high temperatures, in aggressive environments. Machines that can withstand a large number of temperature cycles are also required.

Under such difficult operating conditions, parts and entire assemblies of many machines and devices wear out very quickly, become cracked and destroyed. For work at high temperatures, refractory metals, such as molybdenum and tungsten, are widely used. Tungsten and molybdenum single crystals obtained by zone melting are used for the manufacture of jet and ramjet engine nozzles, rocket head skins, ion engines, turbines, nuclear power plants and many other devices and mechanisms. Polycrystalline tungsten and molybdenum are used for the manufacture of anodes, cathodes, filaments in lamps, and high-temperature electric furnaces.

7. Quartz. This is silicon dioxide, one of the most common minerals in the earth's crust, essentially sand. Natural quartz crystals range in size from grains of sand to several tens of centimeters; there are crystals up to one meter or more in size. Pure quartz crystal is colorless. Minor foreign impurities cause varied colors. Transparent colorless crystals are rock crystal, purple ones are amethyst, smoky ones are rauchtopaz. The optical properties of quartz have led to its widespread use in optical instrument making: prisms for spectrographs and monochromators are made from it. Quartz, unlike glass, transmits ultraviolet radiation well, so special lenses used in ultraviolet optics are made from it.

Quartz also has piezoelectric properties, i.e. capable of converting mechanical stress into electrical voltage. Thanks to this property, quartz is widely used in radio engineering and electronics - in frequency stabilizers (including watches), all kinds of filters, resonators, etc. Quartz crystals are used to excite (and measure) small mechanical and acoustic influences.

Crucibles, vessels and other containers for chemical laboratories are made from fused quartz.

4. Methods for increasing the strength of solids

Polycrystalline steel frames of buildings and bridges, railway rails, machine tools, machine and aircraft parts. The values of real and theoretical strength differ by tens, even hundreds of times. The reason lies in the presence of internal and surface defects in the crystal lattices.

To obtain high-strength materials, it is necessary to grow single crystals that are as defect-free as possible. This is a very difficult task. Most modern methods of strengthening materials are based on a different method: barriers to the movement of defects are created in the crystal. They can be dislocations (violations of the order of arrangement of atoms in the crystal lattice) and other specially created defects.

Examples of point dislocations - violations of the order of arrangement of atoms in a crystal

Such methods include, for example:

– steel alloying: small additions of chromium or tungsten are introduced into the melt, and the strength increases three times;

– high-speed crystallization: the faster the heat is removed from the solidified ingot, the smaller the crystal sizes. At the same time, physical and mechanical characteristics are improved. To quickly remove heat, the molten metal is sprayed into fine dust with a jet of neutral gas, which is then compressed at high pressure and temperature.

The article was prepared with the support of the AVERS company. Reliability and quality are the motto of the AVERS company. The AVERS company specializes in a range of works on water supply to private and collective facilities, therefore each order must be completed in good faith. By going to the section: “drilling deep wells”, you can find out about the services and promotions provided by the AVERS company, and also order a call back to contact a specialist who can answer your questions. The AVERS company employs only highly qualified specialists with extensive experience in working with clients.

Increasing the strength of crystalline bodies results in a gain in the size of various units, reduces their mass, increases operating temperature and increases service life.

5. Consolidation

Students are asked to fill out the test table “Use of crystals in technology.” At the end of the lesson, as a result of the students’ independent work, an express newspaper drawn by two students during the lesson is shown.

Literature

Textbook "Physics-10": Ed. A.A. Pinsky. – M: Education, 2001.

Physical Encyclopedia, vol. 3: Ed. A.M. Prokhorova. – M: Soviet Encyclopedia, 1990.

Internet resources.

Irina Aleksandrovna Dorogovtseva is a graduate of the Komsomolsk-on-Amur State Pedagogical Institute (1997), a physics teacher of the highest qualification category, 8 years of teaching experience. Participant in the finals of the professional competition “Teacher of the Year 2003”. Daughter is 4 years old. He is interested in computer design, programming, and science fiction.

In nature, single crystals of most substances without cracks, impurities and other defects are extremely rare. This has led to many crystals being called gemstones by people over thousands of years. Diamond, ruby, sapphire, amethyst and other precious stones have long been highly valued by people, mainly not for special mechanical or other physical properties, but only because of their rarity.

The development of science and technology has led to the fact that many precious stones or simply crystals rarely found in nature have become very necessary for the manufacture of parts of devices and machines, for scientific research. The demand for many crystals has increased so much that it was impossible to satisfy it by expanding the scale of production of old and searching for new natural deposits.

In addition, many branches of technology and especially scientific research increasingly require single crystals of very high chemical purity with a perfect crystal structure. Crystals found in nature do not meet these requirements, since they grow in conditions that are very far from ideal.

Thus, the task arose of developing a technology for the artificial production of single crystals of many elements and chemical compounds.

The development of a relatively simple method of making a “gem” leads to the fact that it ceases to be precious. This is explained by the fact that most precious stones are crystals of chemical elements and compounds widespread in nature. Thus, diamond is a carbon crystal, ruby and sapphire are aluminum oxide crystals with various impurities.

Let's consider the main methods of growing single crystals. At first glance, it may seem that crystallization from a melt is very simple. It is enough to heat the substance above its melting point, obtain a melt, and then cool it. In principle, this is the correct way, but if special measures are not taken, then at best you will end up with a polycrystalline sample. And if the experiment is carried out, for example, with quartz, sulfur, selenium, sugar, which, depending on the rate of cooling of their melts, can solidify in a crystalline or amorphous state, then there is no guarantee that an amorphous body will not be obtained.

In order to grow one single crystal, slow cooling is not enough. It is necessary to first cool one small area of the melt and obtain a “nucleation” of a crystal in it, and then, sequentially cooling the melt surrounding the “nucleation”, allow the crystal to grow throughout the entire volume of the melt. This process can be achieved by slowly lowering a crucible containing the melt through an opening in a vertical tube furnace. The crystal nucleates at the bottom of the crucible, since it first enters the region of lower temperatures, and then gradually grows throughout the entire volume of the melt. The bottom of the crucible is specially made narrow, pointed to a cone, so that only one crystalline nucleus can be located in it.

This method is often used to grow crystals of zinc, silver, aluminum, copper and other metals, as well as sodium chloride, potassium bromide, lithium fluoride and other salts used in the optical industry. In one day you can grow a rock salt crystal weighing about a kilogram.

The disadvantage of the described method is contamination of the crystals by the crucible material.

The crucibleless method of growing crystals from a melt, which is used to grow, for example, corundum (rubies, sapphires), does not have this drawback. The finest aluminum oxide powder from grains 2-100 microns in size is poured out in a thin stream from the hopper, passes through an oxygen-hydrogen flame, melts and falls in the form of drops onto a rod of refractory material. The temperature of the rod is maintained slightly below the melting point of aluminum oxide (2030°C). Drops of aluminum oxide cool on it and form a crust of sintered corundum mass. Clock mechanism slow (10-20mm/h ) lowers the rod, and an uncut corundum crystal gradually grows on it.

As in nature, obtaining crystals from solution comes down to two methods. The first of these consists of slowly evaporating the solvent from a saturated solution, and the second of slowly decreasing the temperature of the solution. The second method is more often used. Water, alcohols, acids, molten salts and metals are used as solvents. A disadvantage of methods for growing crystals from solution is the possibility of contamination of the crystals with solvent particles.

The crystal grows from those areas of the supersaturated solution that immediately surround it. As a result, the solution near the crystal turns out to be less supersaturated than far from it. Since a supersaturated solution is heavier than a saturated one, there is always an upward flow of “used” solution above the surface of the growing crystal. Without such stirring of the solution, crystal growth would quickly cease. Therefore, the solution is often additionally stirred or the crystal is fixed on a rotating holder. This allows you to grow more advanced crystals.

The lower the growth rate, the better the crystals obtained. This rule applies to all growing methods. Sugar and table salt crystals can be easily obtained from an aqueous solution at home. But, unfortunately, not all crystals can be grown so easily. For example, the production of quartz crystals from solution occurs at a temperature of 400°C and a pressure of 1000 atm .

The applications of crystals in science and technology are so numerous and varied that they are difficult to list. Therefore, we will limit ourselves to a few examples.

The hardest and rarest of natural minerals is diamond. In the entire history of mankind, only about 150 tons of it have been mined, although the global diamond mining industry now employs almost a million people. Today, a diamond is primarily a working stone, not a decoration stone. About 80% of all natural diamonds mined and all artificial diamonds are used in industry. The role of diamonds in modern technology is so great that, according to American economists, stopping the use of diamonds would lead to a halving of the US industrial capacity.

Approximately 80% of diamonds used in technology are used for sharpening tools and cutters of “superhard alloys”. Diamonds serve as supporting stones (bearings) in high-end chronometers for marine vessels and in other highly precise navigational instruments. Diamond bearings show no signs of wear even after 25,000,000 revolutions.

Somewhat inferior to diamond in hardness, ruby competes with it in the variety of technical applications - noble corundum, aluminum oxide Al 2 O 3 with a coloring admixture of chromium oxide. From 1 kg of synthetic ruby it is possible to produce about 40,000 watch support stones. Ruby rods turned out to be irreplaceable in factories producing fabrics from chemical fiber. To produce 1 m of artificial fiber fabric, hundreds of thousands of meters of fiber are required. Thread guides made of the hardest glass wear out in a few days when artificial fiber is pulled through them, agate thread guides can last up to two months, ruby thread guides turn out to be almost eternal.

A new area for the widespread use of rubies in scientific research and technology opened up with the invention of the ruby laser - a device in which a ruby rod serves as a powerful source of light, emitted in the form of a thin beam of light.

An exceptional role has been played by crystals in modern electronics. Most semiconductor electronic devices are made from germanium or silicon crystals.

The uses of crystals in science and technology are so numerous and varied that they are difficult to list. Therefore, we will limit ourselves to a few examples.

The hardest and rarest of natural minerals is diamond. Today, a diamond is primarily a working stone, not a decoration stone.

Due to its exceptional hardness, diamond plays a huge role in technology. Diamond saws are used to cut stones. A diamond saw is a large (up to 2 meters in diameter) rotating steel disk, on the edges of which cuts or notches are made. Fine diamond powder mixed with some adhesive substance is rubbed into these cuts. Such a disk, rotating at high speed, quickly saws any stone.

Diamond is of enormous importance when drilling rocks and in mining operations.

Diamond points are inserted into engraving tools, dividing machines, hardness testing apparatus, and drills for stone and metal.

Diamond powder is used to grind and polish hard stones, hardened steel, hard and super-hard alloys. The diamond itself can only be cut, polished and engraved with diamond. The most critical engine parts in automotive and aircraft production are processed with diamond cutters and drills.

Ruby and sapphire are among the most beautiful and most expensive of precious stones. All these stones have other qualities, more modest, but useful. Blood-red ruby and blue sapphire are siblings; they are generally the same mineral - corundum, aluminum oxide. Corundum with all its varieties is one of the hardest stones on Earth, the hardest after diamond. Corundum can be used to drill, grind, polish, sharpen stone and metal. Grinding wheels, whetstones, and grinding powders are made from corundum and emery.

The entire watch industry runs on artificial rubies. In semiconductor factories, the finest circuits are drawn with ruby needles.

In the textile and chemical industries, ruby thread guides draw threads from artificial fibers, nylon, and nylon.

The new life of ruby is a laser or, as it is called in science, an optical quantum generator (OQG), a wonderful device of our days. In 1960, the first ruby laser was created. It turned out that the ruby crystal amplifies the light. The laser shines brighter than a thousand suns.

A powerful laser beam has enormous power. It easily burns through sheet metal, welds metal wires, burns through steel pipes, and drills the thinnest holes in hard alloys and diamond. Lasers are also used in eye surgery. New laser crystals have also appeared: fluorite, garnets, gallium arsenide, etc.

Sapphire is transparent, so plates for optical instruments are made from it.

The bulk of sapphire crystals goes to the semiconductor industry.

Flint, amethyst, jasper, opal, chalcedony are all varieties of quartz. Small grains of quartz form sand. And the most beautiful, most wonderful variety of quartz is rock crystal, i.e. transparent quartz crystals. Therefore, lenses, prisms and other parts of optical instruments are made from transparent quartz.

The electrical properties of quartz are especially amazing. If you compress or stretch a quartz crystal, electrical charges appear on its edges. This is the piezoelectric effect in crystals.

Nowadays, not only quartz is used as piezoelectrics, but also many other, mostly artificially synthesized substances.

Piezoelectric crystals are widely used to reproduce, record and transmit sound.

There are also piezoelectric methods for measuring blood pressure in human blood vessels and the pressure of juices in the stems and trunks of plants.

Polycrystalline material, Polaroid, has also found its application in technology.

Polaroid is a thin transparent film completely filled with tiny transparent needle-shaped crystals of a substance. Polaroid films are used in polaroid glasses. Polaroids cancel out the glare of reflected light, allowing all other light to pass through. They are indispensable for polar explorers, who constantly have to look at the dazzling reflection of the sun's rays from an icy snow field.

Polaroid glasses will help prevent collisions with oncoming cars, which very often occur due to the fact that the lights of an oncoming car blind the driver, and he does not see this car.

Crystals played an important role in many technological innovations of the 20th century.

Semiconductor devices, which revolutionized electronics, are made from crystalline substances, mainly silicon and germanium. Semiconductor diodes are used in computers and communications systems, transistors have replaced vacuum tubes in radio engineering, and solar panels placed on the outer surface of spacecraft convert solar energy into electrical energy.

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Research

CRYSTALS AND THEIR APPLICATIONS

Author of the work: Krivosheev Evgeniy

student 7 "B" class MBOUSOSH No. 1

Zavitinsk, Amur Region

Head of work: Konchenko N.S.

physics teacher MBOUSOSH No. 1

Zavitinsk, Amur Region

Zavitinsk

2013

Introduction
1. Crystal. Its properties, structure and form
2. Liquid crystals
3. Application of LCD
4. Application of crystals in science and technology
5. Practical part
Conclusion
Bibliography
Introduction
Relevance of the work:
Since crystals are widely used in science and technology, it is difficult to name a branch of production where crystals are not used. Therefore, knowing and understanding the properties of crystals is very important for every person.
Purpose of the study: Growing a crystal from a solution at home, studying the practical applications of crystals in science and technology.
Tasks:
1. Study of the theory of crystals.
2. Study of material on growing a crystal under normal conditions and in laboratory conditions.
3.Observation of crystal formation.
4.Description of observations.
5. Study of the application of crystals in modern life.

1. Crystal. Its properties, structure and form

The word "crystal" comes from the Greek " crustallos", that is, "ice". Solids whose atoms or molecules form an ordered periodic structure (crystal lattice).

Crystal formation.

Crystals are formed in three ways: from melt, from solution and from vapor. An example of crystallization from a melt is the formation of ice from water. crystal liquid growing laboratory

In the world around us, one can often observe the formation of crystals directly from a gaseous environment, from solutions and from a melt. On a quiet frosty night under a clear sky, in the bright light of the moon or a lantern, we sometimes see slowly descending flakes of frost glistening with sparks. These are plate-like ice crystals that form right next to us from moist and cooled air.

The structure of solids depends on the conditions under which the transition from liquid to solid occurs. If such a transition occurs very quickly, for example, with a sharp cooling of the liquid, then the particles do not have time to line up in the correct structure and a fine-crystalline body is formed. When the liquid is slowly cooled, large and regularly shaped crystals are obtained. In some cases, in order for a substance to crystallize, it must be kept at different temperatures. External pressure also affects crystal growth. In addition, a significant part of the crystals that had a perfect cut in the distant past managed to lose it under the influence of water, wind, and friction with other solids. Thus, many rounded transparent grains that can be found in coastal sand are quartz crystals that have lost their edges as a result of prolonged friction against each other.

Crystal structure

The variety of crystals in shape is very large.

Crystals can have from four to several hundred facets. But at the same time, they have a remarkable property - whatever the size, shape and number of faces of the same crystal, all flat faces intersect with each other at certain angles. The angles between corresponding faces are always the same. The shape is influenced by factors such as temperature, pressure, frequency, concentration and direction of movement of the solution. Therefore, crystals of the same substance can exhibit a wide variety of forms.

Rock salt crystals, for example, can have the shape of a cube, parallelepiped, prism, or a body of a more complex shape, but their faces always intersect at right angles. The faces of quartz are shaped like irregular hexagons, but the angles between the faces are always the same - 120°.

The law of constancy of angles, discovered in 1669 by the Dane Nikolai Steno, is the most important law of the science of crystals - crystallography.

Measuring the angles between the faces of crystals is of very great practical importance, since from the results of these measurements in many cases the nature of the mineral can be reliably determined.

The simplest device for measuring crystal angles is an applied goniometer.

Types of crystals

In addition, a distinction is made between single crystals and polycrystals.

A single crystal is a monolith with a single undisturbed crystal lattice. Natural single crystals of large sizes are very rare.

Single crystals include quartz, diamond, ruby and many other precious stones.

Most crystalline solids are polycrystalline, that is, they consist of many small crystals, sometimes visible only under high magnification.

All metals are polycrystals.

2. Liquid crystals

Liquid crystal - this is a special state of matter, intermediate between liquid and solid states. In a liquid, molecules can rotate freely and move in any direction. In a liquid crystal there is some degree of geometric order in the arrangement of molecules, but some freedom of movement is also allowed.

The consistency of liquid crystals can be different - from easily flowing liquid to paste-like. Liquid crystals have unusual optical properties, which are used in technology. Liquid crystals are formed from molecules with different geometric shapes. such as color, transparency, etc. Numerous applications of liquid crystals are based on all this.

3. Application of LCD

The arrangement of molecules in liquid crystals changes under the influence of factors such as temperature, pressure, electric and magnetic fields; changes in the arrangement of molecules lead to changes in optical properties, such as color, transparency and the ability to rotate the plane of polarization of transmitted light. Numerous applications of liquid crystals are based on all this. For example, the dependence of color on temperature is used for medical diagnostics. By applying certain liquid crystal materials to the patient's body, the doctor can easily identify diseased tissues by color changes in places where these tissues generate increased amounts of heat. The temperature dependence of color also allows you to control the quality of products without destroying them. If a metal product is heated, its internal defect will change the temperature distribution on the surface. These defects are identified by changes in the color of the liquid crystal material applied to the surface.

Thin films of liquid crystals sandwiched between glasses or sheets of plastic have found widespread use as indicator devices. Liquid crystals are widely used in the production of wristwatches and small calculators. Flat-panel televisions with thin liquid crystal screens are being created.

4. Application of crystals in science and technology

Nowadays, crystals have very wide applications in science, technology and medicine.

Diamond saws are used to cut stones. A diamond saw is a large (up to 2 meters in diameter) rotating steel disk, on the edges of which cuts or notches are made. Fine diamond powder mixed with some adhesive substance is rubbed into these cuts. Such a disk, rotating at high speed, quickly saws any stone.

Diamond is of great importance when drilling rocks and in mining operations. Diamond points are inserted into engraving tools, dividing machines, hardness testing apparatus, and drills for stone and metal. Diamond powder is used to grind and polish hard stones, hardened steel, hard and super-hard alloys. The diamond itself can only be cut, polished and engraved with the diamond itself. The most critical engine parts in automotive and aircraft production are processed with diamond cutters and drills.

Corundum can be used to drill, grind, polish, sharpen stone and metal. Grinding wheels and whetstones, grinding powders and pastes are made from corundum and emery. In semiconductor factories, the finest circuits are drawn with ruby needles.

Garnet is also used in the abrasive industry. Grinding powders, grinding wheels, and skins are made from garnets. They sometimes replace ruby in instrument making.

Lenses, prisms and other parts of optical instruments are made from transparent quartz. The artificial “mountain sun” is a device widely used in medicine. When turned on, this device emits ultraviolet light, these rays are healing. The lamp in this device is made of quartz glass. A quartz lamp is used not only in medicine, but also in organic chemistry, mineralogy, and helps distinguish counterfeit stamps and banknotes from real ones. Pure, defect-free rock crystals are used in the manufacture of prisms, spectrographs, and polarizing plates.

Fluorite is used to make lenses for telescopes and microscopes, to make spectrograph prisms and in other optical instruments.

5. Practical part

Growing copper sulfate crystals.

Copper sulfate is copper sulfate pentahydrate, as the large crystals resemble colored blue glass. Copper sulfate is used in agriculture to control pests and plant diseases, in industry in the production of artificial fibers, organic dyes, mineral paints, and arsenic chemicals.

Method of growing at home:

1) First, prepare a solution of concentrated vitriol. After this, slightly heat the mixture to ensure complete dissolution of the salt. To do this, place the glass in a pan with warm water.

2) Pour the resulting concentrated solution into a jar or beaker; We will also hang a crystalline “seed” there on a thread - a small crystal of the same salt - so that it is immersed in the solution. It is on this “seed” that the future exhibit of your crystal collection will grow.

3) Place the container with the solution open in a warm place. When the crystal grows large enough, remove it from the solution, dry it with a soft cloth or paper napkin, cut the thread and cover the edges of the crystal with colorless varnish to protect it from “weathering” in the air.

Observation of the growth process of copper sulfate crystals.

To begin with, we poured a solution of copper sulfate into a beaker and tied a seed to a thread. And they dropped the crystal into the glass. The very next day we had a fairly large polycrystal, about 2 centimeters in length. The crystal itself was very uneven, with small columns. Crystallization did not continue further, no matter how long we waited.

But we didn’t stop there and made two more crystals of copper sulfate. We only took the seed from the column of the failed crystal. In one solution the temperature was constantly changing, while in the other glass it was constant. After a few days, we got two full-fledged single crystals of copper sulfate. They turned out to have smooth edges, absolutely symmetrical. So I realized that in order to make a smooth crystal, the seed must also be smooth and symmetrical.

Observing the process of crystal growth in salt solutions under a microscope.

Examining crystals under a microscope is very interesting, since the “younger” the crystal, the more regular its shape. Studying crystals under a microscope does not take much time and resources: only a few grams of salt are needed to prepare the solution, and it does not take much time for the crystal to grow.

A few drops of a saturated solution of various salts were applied to a microscope slide. The glass was slightly heated with a spirit lamp and placed on the microscope stage. By moving the slide and adjusting the magnification, we achieved such a position that the drop occupied the entire field of view of the microscope. After a short period of time (about 1 min), crystallization began at the edge of the drop, where it dries faster. The resulting small crystals formed a continuous opaque crust at the edges of the drop, which appears dark in transmitted light. Gradually, from this mass of crystals, individual tips of individual crystals began to emerge, directed into the drop, which, growing, formed various shapes. Most often, new crystallization centers in the free space inside the droplet, as a rule, did not spontaneously arise. After some time, the entire field of view was filled with crystals, and crystallization was almost complete.

Conclusion

Thus, crystals are one of the most beautiful and mysterious creations of nature. We live in a world consisting of crystals, we build with them, process them, eat them, heal with them... The science of crystallography deals with the study of the variety of crystals. She comprehensively examines crystalline substances, studies their properties and structure. In ancient times, crystals were considered to be rare. Indeed, the discovery of large homogeneous crystals in nature is a rare phenomenon. However, finely crystalline substances are quite common. For example, almost all rocks: granite, sandstone, limestone are crystalline. Even some parts of the body are crystalline, for example, the cornea of the eye, vitamins, and the sheath of nerves. The long path of searches and discoveries, from measuring the external shape of crystals deep into the subtleties of their atomic structure, has not yet been completed. But now researchers have studied its structure quite well and are learning to control the properties of the crystals.

As a result of the work done, I can draw the following conclusions:

1. A crystal is a solid state of matter. It has a certain shape and a certain number of edges.

2. Crystals come in different colors, but most are transparent.

3. Crystals are not a museum rarity at all. Crystals surround us everywhere. The solids from which we build houses and make machines, the substances that we use in everyday life - almost all of them belong to crystals. Sand and granite, table salt and sugar, diamond and emerald, copper and iron - all these are crystalline bodies.

4. The most valuable among crystals are gems.

5. I grew a crystal at home from a saturated solution of copper sulfate.

Thus, the goals and objectives that I outlined at the beginning of my work have been achieved. As a result of the work, I experimentally found evidence for the assumption that was made by the English crystallographer Frank about the stepwise growth of crystals.

The work done was very interesting and entertaining. I would also like to grow crystals from other substances, because there are so many of them around us...

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Application of crystals. Main applications of artificial crystals

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Author of the work: Krivosheev Evgeniy

student 7 "B" class MBOUSOSH No. 1

Zavitinsk, Amur Region

Head of work: Konchenko N.S.

physics teacher MBOUSOSH No. 1

Zavitinsk, Amur Region

Zavitinsk

2013

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