Application of crystals in science and technology. Application of artificial crystals

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.

Due to its exceptional hardness, diamond plays a huge role in technology. Diamond saws are used to cut stones. 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.

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). In 1960 The first ruby laser was created. It turned out that the ruby crystal amplifies the light. For a ruby laser, the smallest diameter of the light spot is approximately 0.7 microns. In this way, extremely high radiation densities can be created. That is, concentrate energy as much as possible. A powerful laser beam with enormous power. It easily burns through sheet metal, welds metal wires, burns through metal pipes, and drills the thinnest holes in hard alloys and diamond. These functions are performed by a solid laser using ruby, garnet and neodite. In eye surgery, neodyne lasers and ruby lasers are most often used. Ground-based short-range systems often use gallium arsenide injection lasers. 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. Therefore, lenses, prisms and other parts of optical instruments are made from transparent quartz. Quartz glass has the following qualities:

High uniformity and good transmittance in the ultraviolet, visible and near-infrared ranges;

No fluorescence;

Low coefficient of thermal expansion;

High resistance to mechanical damage and thermal shock;

Low bubble.

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, mainly artificially synthesized substances: blue salt, barium titanate, potassium and ammonium dihydrogen phosphates (KDP and ADP) and many others.

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. Piezoelectric plates measure, for example, the pressure in the barrel of an artillery gun when fired, the pressure at the moment of a bomb explosion, instantaneous pressure in engine cylinders when hot gases explode in them .

The polycrystalline material Polaroid has also found its use in technology.

Polaroid is thin transparencies, completely filled with tiny transparent needle-shaped crystals of a substance that birefringents and polarizes light. All crystals are located parallel to each other, so they all equally polarize the light passing through the film.

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.

Liquid crystals

Liquid crystals are substances that simultaneously have the properties of both liquids (fluidity) and crystals (anisotropy). In terms of structure, liquid crystals are jelly-like liquids, consisting of elongated molecules, ordered in a certain way throughout the entire volume of this liquid. The most characteristic property of LCs is their ability to change the orientation of molecules under the influence of electric fields, which opens ample opportunities for their use in industry. Based on their type, liquid crystals are usually divided into two large groups: nematics and smectics. In turn, nematics are divided into nematic and cholesteric liquid crystals.

One of the important areas of use of liquid crystals is thermography. By selecting the composition of the liquid crystalline substance, indicators are created for different temperature ranges and for various designs. For example, liquid crystals in the form of a film are applied to transistors, integrated circuits and printed circuit boards of electronic circuits. Faulty elements - very hot or cold, not working - are immediately noticeable by bright color spots. Doctors have received new opportunities: a liquid crystal indicator on the patient’s skin quickly diagnoses hidden inflammation and even a tumor.

Liquid crystals are used to detect harmful vapors chemical compounds and gamma and ultraviolet radiation hazardous to human health. Pressure meters and ultrasound detectors have been created based on liquid crystals. But the most promising area of application of liquid crystalline substances is information technology. Only a few years have passed from the first indicators, familiar to everyone from digital watches, to color televisions with LCD screens the size of a postcard. Such televisions provide an image that is very High Quality, consuming less energy.

The operation of any LCD panel is based on the principle of changing transparency (more precisely, changing the polarization of transmitted light) of liquid crystals under the influence of electric current. In a TFT matrix, a layer of liquid crystals is controlled by a matrix of microscopic transistor analog switches, one switch for each pixel of the image, which makes it possible to achieve a high speed of switching dots on and off and increase image contrast. Since liquid crystals themselves do not have color, the color panel contains three layers of liquid crystals (or a special single-layer mosaic structure) with corresponding light filters for each color component (red, green, blue). Liquid crystals cannot glow themselves, so in order to give the screen the usual glowing appearance, a special flat lamp is installed behind the LCD panel, illuminating the screen from the back side. As a result, it seems to the user that the matrix “glows”, like a regular CRT screen.

Types of etching: dry (plasma) and liquid (in liquid etchants, HF acid). Advantages dry etching: the ability to control anisotropy, the ability to control selectivity, weak dependence of etching on the adhesion of the protective mask to the substrate, does not require subsequent washing and drying operations, more economical than etching in liquid reagents. Flaws: damage to the surface of materials due to bombardment by ions, electrons and photons. Dry etching is divided into:

Main characteristics of dry etching: anisotropy– the ratio of the rate of etching of the working material normal to the surface of the plate to the rate of its lateral etching; selectivity– the ratio of the etching rates of various materials (for example, a worker and a mask) under the same conditions.

Ion etching– a process in which surface layers of materials are removed only by physical spraying. Sputtering is carried out by energetic ions of gases that do not enter into chemical reactions with the material being processed (usually ions of inert gases). If the material being processed is placed on electrodes or holders in contact with the discharge plasma, then etching under such conditions is called ion-plasma. If the material is placed in a vacuum processing zone, separated from the plasma area, then etching is called ion beam etching.

IN plasmachemical In etching, the surface layers of materials are removed only as a result of chemical reactions between chemically active particles and atoms of the etched substance. If the material being processed is in the discharge plasma region, then etching is called plasma. In this case, chemical etching reactions on the surface of the material will be activated by bombardment of low-energy electrons and ions, and also photon bombardment. If the material is located in a vacuum processing zone, usually called the reaction zone and separated from the plasma region, then etching is carried out with chemically active particles without activation by electron and ion bombardment, and in some cases, in the absence of exposure to photons. This etching is called radical.

Plasma is used in three main processes: for etching materials, for sputtering thin films (other materials) onto the surface of materials, and for doping (implanting) other particles inside the material.

Modern application of plasma technologies. The main process in photolithography technology (metal etching, plasma ashing, plasma de-scum (resist removal))! Also used in creation technologies: NEMS, MEMS, microelectronics, nanoelectronics, gyroscopes, accelerometers, polymer etching, polymer microstructures, ceramic microstructures, deep etching technologies (with high aspect ratio: the ratio between the size of a characteristic element and the etching depth).

Applications of crystals in science and technology The applications of crystals in science and technology are so numerous and varied that they are difficult to list.

Diamond The hardest and rarest of natural minerals, diamond. Today, a diamond is primarily a worker 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 kind of adhesive substance is rubbed into these cuts. Such a disk, rotating with 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 A 12 O 3. The difference in color arose due to very small impurities in aluminum oxide: an insignificant addition of chromium turns colorless corundum into blood red ruby, titanium oxide into sapphire. There are corundums of other colors. They also have a modest, nondescript brother: brown, opaque, fine corundum emery, which is used to clean the metal from which sandpaper is made. Corundum, with all its varieties, is one of the hardest stones on Earth, the hardest after diamond.

A powerful laser beam with enormous power. It easily burns through sheet metal, welds metal wires, burns through metal pipes, and drills the thinnest holes in hard alloys and diamond. These functions are performed by a solid laser, which uses ruby, garnet and neodite. In eye surgery, neodyne lasers and ruby lasers are most often used. In ground-based short-range systems, gallium arsenide injection lasers are often used.

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, that is, 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, mainly artificially synthesized substances: synthetic salt, barium titanate, potassium and ammonium dihydrogen phosphates (KDA and ADR) and many others. 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. Piezoelectric plates are used to measure, for example, the pressure in the barrel of an artillery gun when fired, the pressure at the moment of a bomb explosion, and the instantaneous pressure in engine cylinders during the explosion of hot gases in them.

The edectro-optical industry is the industry of crystals that do not have a center of symmetry. This industry is very large and diverse; its factories grow and process hundreds of types of crystals for use in optics, acoustics, radio electronics, and laser technology.

The polycrystalline material Polaroid has also found its use in technology. Polaroid is a thin transparent film, completely filled with tiny transparent needle-shaped crystals of a substance that birefringes and polarizes light. All crystals are located parallel to each other, so they all equally polarize the light passing through the film. 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 sun rays from behind an icy snow field.

Polaroid glasses will help prevent collisions with oncoming cars, which very often happen because the lights of the oncoming car blind the driver, and he does not see this car. If the windshields of cars and the glasses of car headlights are made of Polaroid, and both fields of the roid are rotated so that their optical axes are shifted, then the windshield will not let in the light of the headlights of an oncoming car, and will “extinguish it”.

Crystals played an important role in many technical innovations of the 20th century. Some crystals generate an electrical charge when deformed. Their first significant application was the manufacture of radio frequency oscillators stabilized by quartz crystals. By causing the quartz plate to vibrate electric field radio frequency oscillating circuit, you can thereby stabilize the receiving or transmitting frequency.

Crystals are also used in some masers to amplify microwave waves and in lasers to amplify light waves. Crystals with piezoelectric properties are used in radio receivers and transmitters, in pickup heads and in sonar. Some crystals modulate light beams, while others generate light under the influence of an applied voltage. The list of uses for crystals is already quite long and is constantly growing.

What are crystals

Crystal (from Greek. krystallos- “transparent ice”) was originally the name given to transparent quartz (rock crystal), found in the Alps. Rock crystal was mistaken for ice, hardened by cold to such an extent that it no longer melts. Initially main feature The crystal was seen in its transparency, and this word was used to apply to all transparent natural solids.

Later they began to produce glass that was not inferior in brilliance and transparency to natural substances. Objects made from such glass were also called “crystal”. Even today, glass of special transparency is called crystal, and the “magic” ball of fortune tellers is called a crystal ball.

Amazing feature rock crystal and many other transparent minerals are due to their smooth, flat faces. At the end of the 17th century. it was noticed that there is a certain symmetry in their arrangement. It was also found that some opaque minerals also have a natural regular cut and that the shape of the cut is characteristic of a particular mineral. A guess arose that the form may be associated with internal structure. Eventually, crystals came to be called all solids that have a naturally flat cut.

Keeping in mind the possibility of directly studying the internal structure, many involved in crystallography began to use the term “crystal” to apply to all solids with an ordered internal structure.

The atoms that make up gases, liquids, and solids have varying degrees of order. In a gas, atoms are not large groups atoms connected into molecules are in constant random motion. If you cool a gas, a temperature is reached at which the molecules move as close to each other as possible and a liquid is formed. But atoms and molecules of a liquid can still slide relative to each other. When some liquids, such as water, are cooled, a temperature is reached at which the molecules freeze into a relatively immobile crystalline state. This temperature, which is different for all liquids, is called the freezing point. (Water freezes at 0°C; in this case, water molecules combine with each other in an orderly manner, forming a regular geometric figure.) Each particle of a substance (atom or molecule) in the crystalline state has the same environment as any other particle of the same type in the entire crystal. In other words, it is surrounded by very specific particles located at very specific distances from it. It is this ordered three-dimensional arrangement that characterizes crystals and distinguishes them from other solids..

The amazing is nearby

Probably the most common and at the same time amazing crystals are snowflakes. Every winter we see billions of these little crystals. And what patterns are formed on the windows (unless, of course, they are plastic).

A snowflake is a complex symmetrical structure consisting of ice crystals collected together. There are many assembly options - so far we have not been able to find two identical snowflakes. Research conducted in Libbrecht's laboratory confirms this fact - crystal structures can be grown artificially or observed in nature.

Crystallography is currently actively developing in connection with the needs of electronics and solid state physics - in particular, the properties of semiconductors used in our everyday electronic devices largely depend on the characteristics of the crystals used in them. The next step in studying the properties of the most famous natural crystals - snowflakes - was made by physics professor Kenneth Libbrecht from the California Institute of Technology.

In Professor Libbrecht's laboratory, snowflakes are grown artificially. “I’m trying to figure out the dynamics of crystal formation at the molecular level,” the professor comments. - This not an easy task, and the ice crystals hide many secrets." To study the characteristics of snowflakes, Professor Libbrecht began in 2001 to take photographs of naturally formed snowflakes and conduct a comparative classification of them. The structure and appearance of snowflakes, as it turned out, depend on where exactly they were observed. According to Libbrecht, the most beautiful and complex snowflakes fall where the climate is harsher - for example, in Alaska, but in New York, where the climate is milder, the structures of snow crystals are much simpler.

Let's admire this miracle

Applications of crystals

The applications of crystals in science and technology are so numerous and varied that they are difficult to list.

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.

And 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

sapphire

They also have a very modest, nondescript brother: brown, opaque, fine corundum - emery used to clean metal, from which sandpaper is made. 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.

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

The bulk of sapphire crystals goes to the semiconductor industry.

jasper

amethyst

flint

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.

The polycrystalline material Polaroid has also found its use in technology.

Polaroid is a thin transparent film completely filled with tiny transparent needle-shaped crystals of a substance that birefringes and polarizes light. All crystals are located parallel to each other, so they all equally polarize the light passing through the film.

Polaroid glasses will help prevent collisions with oncoming cars, which very often occur due to the fact that the lights of the oncoming car blind the driver, and he does not see this car. If the windshields of cars and the glass of car headlights are made of Polaroid, and both polaroids are rotated so that their optical axes are shifted, then the windshield will not let in the light of the headlights of an oncoming car, and will “extinguish it.”

Crystals played an important role in many technical innovations of the 20th century. Some crystals generate an electrical charge when deformed.

Semiconductor devices, which revolutionized electronics, are made from crystalline substances, mainly silicon and germanium.
The list of uses for crystals is already quite long and is constantly growing.

Crystals and health

There are quite a few methods of using crystals in therapy. The simplest is contact healing. You apply a stone to the sore spot or wear jewelry made from it. Such jewelry for medicinal purposes can be used throughout the day, depending on your disease.

Green stones

All green stones are calming and relieve insomnia.

Emerald helps strengthen vision and can cure coughs.

Jade - useful for kidney diseases. It must be worn on the lower back for a year.

Malachite strengthens the immune system, helps the functioning of the pancreas, kidneys and spleen. It is believed that a malachite pendant in a copper frame cures rheumatism and radiculitis. Malachite works very well with silver.

Blue and purple stones

These tones relieve inflammation, fight infections, and are useful for those who spend a lot of time at the computer or for lung diseases. Stones of blue color reduce appetite.

Turquoise serves as an indicator of health: if you wear turquoise jewelry and see that it has darkened, this is a sure sign of an incipient illness.

Fetisov Nikolay

The world around us consists of crystals; we can say that we live in a world of crystals. Residential buildings and industrial structures, airplanes and rockets, motor ships and diesel locomotives, rocks and minerals are composed of crystals. We eat crystals, we heal with them, and we are partly made of crystals.

So what are crystals? What properties do they have? How do crystals grow? How and where are they currently used and what are the prospects for their use in the future? These questions interested me, and I tried to find answers to them.

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11TH SCIENTIFIC AND PRACTICAL CONFERENCE OF KUZNETSK DISTRICT “OPEN WORLD”

PHYSICS SECTION

Main applications of artificial crystals

Completed by an 8th grade student

Fetisov Nikolay

Head Sizochenko A.I.,

Physics teacher

Municipal secondary education

Establishment

"Basic general education

School No. 24"

Novokuznetsk, 2014

Introduction……………………………………………………2

1. Main part

1.1. The concept of crystal………………...………..……..4

1.2. Single crystals and polycrystals........................4

1.3. Methods for growing crystals………….…5

1.4. Application of crystals…………………..…...…7

2. Practical part

2.1. Growing crystals at home

Conditions…………………………………………...9

3. Conclusion………………………………………….…11

Bibliography..………………………………………………………………...13

Applications………………………….………………………..14-15

Introduction

Like a magical sculptor

Light edges of crystals

Makes a colorless solution.

N.A.Morozov

Crystals are substances in which the smallest particles are “packed” in a certain order. As a result, as crystals grow, flat edges spontaneously appear on their surface, and the crystals themselves take on a variety of geometric shapes.

Statement by Academician A.E. Fersman “Almost the entire world is crystalline. The world is ruled by the crystal and its solid, linear laws” is consistent with the scientific interest of scientists around the world in this object of research.

Modern industry cannot do without a wide variety of crystals. They are used in watches, transistor radios, computers, lasers and much more. The great laboratory - nature - can no longer satisfy the demand of developing technology, and so artificial crystals are grown in special factories: small, almost imperceptible, and large ones weighing several kilograms.

People have learned to obtain many precious stones artificially. For example, bearings for watches and other precision instruments have long been made from artificial rubies. Beautiful crystals are also obtained artificially, which do not exist in nature at all - cubic zirconia. It is difficult to distinguish cubic zirconias from diamonds by eye - they play so beautifully in the light.

My work is research, since its implementation uses the knowledge of several educational subjects: physics, chemistry, biology, computer science. As a result of my activities, I created a presentation “Crystals and their applications”, which can be used in physics and chemistry lessons as a visual aid, and grown crystals from copper sulfate and table salt.

Target:

Determine the main areas of application of artificial crystals and test experimentally the possibility of growing crystals of table salt and copper sulfate without the use of special equipment.

To achieve this goal, I faced the following

tasks:

Collect material about crystals and their properties from literary and Internet sources.
Conduct experiments on growing crystals of copper sulfate and table salt.
Systematize material about crystals: the use of artificial crystals and methods of growing them.
Create a presentation “Crystals and their applications” for educational purposes.

Main part

Crystal concept

Crystal (from the Greek krystallos - “transparent ice”) was originally called transparent quartz (rock crystal), found in the Alps. Rock crystal was mistaken for ice, hardened by cold to such an extent that it no longer melts. Initially, the main characteristic of a crystal was seen in its transparency, and this word was used to apply to all transparent natural solids. Later they began to produce glass that was not inferior in brilliance and transparency to natural substances. Objects made from such glass were also called “crystal”. Even today, glass of special transparency is called crystal, and the “magic” ball of fortune tellers is called a crystal ball.

An amazing feature of rock crystal and many other transparent minerals is their smooth, flat edges. At the end of the 17th century. it was noticed that there is a certain symmetry in their arrangement and it was found that some opaque minerals have a natural regular cut. A guess arose that the shape may be related to the internal structure. Eventually, crystals came to be called all solids that have a naturally flat cut.

In the armory there are clothes and crowns of Russian tsars, completely strewn with crystals - gems - amethysts. In churches, icons and altars were decorated with amethysts.

The most famous crystals are diamonds, which, after cutting, turn into diamonds. People have been trying to unravel the mystery of these stones for many centuries, and when they established that diamond is a type of carbon, no one believed it.

The decisive experiment was carried out in 1772 by the French chemist Lavoisier. In nature, diamonds are formed in the bowels of the earth at very high temperatures ah and pressure. Scientists were able to create conditions in the laboratory under which diamonds can be obtained from graphite only 200 years later. Tens of tons of artificial diamonds are now produced. Among them there are diamonds for jewelry purposes, but the bulk of them are used to make various tools.

Single crystals and polycrystals

Crystalline bodies can be single crystals or polycrystals. A single crystal is called a single crystal, having a macroscopic ordered crystal lattice. They have a geometrically regular external shape, but this feature is not mandatory.

Polycrystals are chaotically oriented small crystals fused together - crystallites.

Crystal growing methods

In the laboratory, crystals are grown under carefully controlled conditions to ensure required properties, but in principle, laboratory crystals are formed in the same way as in nature - from a solution, melt or vapor. Thus, piezoelectric crystals of Rochelle salt are grown from an aqueous solution at atmospheric pressure. Large crystals of optical quartz are also grown from solution, but at temperatures of 350–450 O C and pressure 140 MPa. Rubies are synthesized at atmospheric pressure from aluminum oxide powder melted at a temperature of 2050 O C. Silicon carbide crystals used as an abrasive are obtained from the fumes in an electric furnace.

The first single crystal obtained in the laboratory was ruby. To obtain ruby, a mixture of anhydrous alumina containing a greater or lesser admixture of caustic potassium with barium fluoride and dichromopotassium salt was heated. The latter is added to color the ruby, and a small amount of aluminum oxide is taken. The mixture is placed in a clay crucible and heated (from 100 hours to 8 days) in reverberatory furnaces at temperatures up to 1500 O C. At the end of the experiment, a crystalline mass appears in the crucible, and the walls are covered with ruby crystals of a beautiful pink color.

The second common method for growing synthetic gemstone crystals is the Czochralski method. It is as follows: the melt of the substance from which the stones are supposed to be crystallized is placed in a refractory crucible made of a refractory metal (platinum, rhodium, iridium, molybdenum, or tungsten) and heated in a high-frequency inductor. A seed from the material of the future crystal is lowered into the melt on an exhaust shaft, and synthetic material is grown on it to the required thickness. The shaft with the seed is gradually pulled upward at a speed of 1-50 mm/h with simultaneous growth at a rotation speed of 30-150 rpm. Rotate the shaft to equalize the temperature of the melt and ensure uniform distribution of impurities. The diameter of the crystals is up to 50 mm, length up to 1 m. Synthetic corundum, spinel, garnets and other artificial stones are grown using the Czochralski method.

Crystals can also grow when vapor condenses - this is how snowflake patterns are obtained on cold glass. When metals are displaced from salt solutions with the help of more active metals, crystals also form. For example, dip an iron nail into a solution of copper sulfate; it will become covered with a red layer of copper. But the resulting copper crystals are so small that they can only be seen under a microscope. Copper is released on the surface of the nail very quickly, so its crystals are too small. But if the process is slowed down, the crystals will turn out to be large. To do this, cover the copper sulfate with a thick layer of table salt, put a circle of filter paper on it, and on top - an iron plate with a slightly smaller diameter. All that remains is to pour a saturated solution of table salt into the vessel. The copper sulfate will begin to slowly dissolve in the brine. Copper ions (in the form of green complex anions) will diffuse upward very slowly over many days; the process can be observed by the movement of the colored border. Having reached the iron plate, copper ions are reduced to neutral atoms. But since this process occurs very slowly, the copper atoms line up into beautiful shiny crystals. Sometimes these crystals form branches - dendrites.

Application of crystals.

Natural crystals have always aroused people's curiosity. Their color, shine and shape touched the human sense of beauty, and people decorated themselves and their homes with them. For a long time, superstitions have been associated with crystals; like amulets, they were supposed to not only protect their owners from evil spirits, but also endow them with supernatural abilities. Later, when the same minerals began to be cut and polished like precious stones, many superstitions were preserved in “lucky” talismans and “own stones” corresponding to the month of birth. All natural gemstones except opal are crystalline, and many of them, such as diamond, ruby, sapphire and emerald, are found as beautifully cut crystals.Crystal jewelryare as popular now as they were during the Neolithic.

Based on the laws of optics, scientists were looking for a transparent, colorless and defect-free mineral from which lenses could be made by grinding and polishing. The necessary optical and mechanical properties have crystals of uncolored quartz, andthe first lenses, including for glasses, were made from them. Even after the advent of artificial optical glass, the need for crystals did not completely disappear; crystals of quartz, calcite and other transparent substances that transmit ultraviolet and infrared radiation, are still used to make prisms and lenses for optical devices.

Crystals played an important role in many technical innovations of the 20th century. Some crystals generate an electrical charge when deformed. Their first significant use wasproduction of radio frequency generators with stabilization by quartz crystals.By forcing a quartz plate to vibrate in the electric field of a radio frequency oscillatory circuit, it is possible to stabilize the receiving or transmitting frequency.

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. Semiconductors are also widely used in AC-DC converters.

Crystals with piezoelectric properties are used in radio receivers and transmitters, in pickup heads and in sonar. Some crystals modulate light beams, while others generate light under the influence of an applied voltage. The list of uses for crystals is already quite long and is constantly growing.

Artificial crystals. For a long time, man has dreamed of synthesizing stones that are as precious as those found in nature. Until the 20th century such attempts were unsuccessful. But in 1902managed to get rubies and sapphires, possessing the properties of natural stones. Later, in the late 1940s there wereemeralds synthesized, and in 1955 the General Electric company and the Physical Institute of the USSR Academy of Sciences reported the productionartificial diamonds.

Many technological needs for crystals have stimulated research into methods for growing crystals with predetermined chemical, physical, and electrical properties. The researchers’ efforts were not in vain, and methods were found to grow large crystals of hundreds of substances, many of which have no natural analogue. In nature, there are often solid bodies that have the shape of regular polyhedra. Such bodies were called crystals. The study of the physical properties of crystals has shown that a geometrically correct shape is not their main feature.

It is completely consistent with the undying scientific interest of scientists around the world and all fields of knowledge in this object of research. At the end of the 60s of the last century, a serious scientific breakthrough began in the fieldliquid crystals, which gave rise to the “indicator revolution” to replace pointer mechanisms with means of visual display of information. Later, the concept of a biological crystal (DNA, viruses, etc.) entered science, and in the 80s of the twentieth century - a photonic crystal.

Practical part

Growing crystals at home

Growing crystals is a very interesting process, but quite lengthy and painstaking.

It is useful to know what processes control its growth; Why different substances form crystals various shapes, and some do not form them at all; what needs to be done to make them big and beautiful.

I tried to find answers to these questions in my work.

If crystallization proceeds very slowly, one large crystal (or single crystal) is obtained; if it is fast, then many small ones are obtained.

I grew crystals at home in different ways.

Method 1 . Cooling a saturated solution of copper sulfate. As the temperature decreases, the solubility of substances decreases and they precipitate. First, tiny crystal nuclei appear in the solution and on the walls of the vessel. When cooling is slow and there are no solid impurities in the solution, many nuclei are formed, and gradually they turn into beautiful crystals of regular shape. With rapid cooling, many small crystals appear, almost none of them have the correct shape, because there are many of them growing and they interfere with each other.

In order to grow a crystal from copper sulfate, I made a supersaturated solution:

1. To do this, I took warm water, dissolved vitriol in it and added it until it stopped dissolving.

2. Pour through a filter (gauze) into another clean container. I poured boiling water over the container to prevent rapid crystallization of the solution on the dirty walls.

3. Prepared the seed.

4. I tied it to a thread and lowered it into the solution.

In order for the crystal to grow evenly on all sides, it is better to keep the seed (small crystal) suspended in the solution. To do this, I made a jumper from a glass rod. By the way, it is advisable to take a smooth, thin thread, perhaps silk, so that unnecessary small crystals do not form on it. Next, I put my solution in a warm place. Slow cooling is very important (to get a large crystal). Crystallization can be seen within a few hours. Periodically you need to change or update the saturated solution, and also clean off small crystals from the thread. (Annex 1)

Method 2 - gradual removal of water from a saturated solution.

In this case, the slower the water is removed, the better the result. I left open a vessel with a solution of table salt ( table salt) at room temperature for 14 days, covering it with a sheet of paper - the water evaporated slowly, and dust did not get into the solution. The growing crystal was suspended in a saturated solution on a thin strong thread. The crystal turned out to be large, but shapeless - amorphous. (Annex 1)

Growing crystals is an interesting process, but it requires a careful and careful approach to your work. Theoretically, the size of the crystal that can be grown at home in this way is unlimited. There are cases when enthusiasts received crystals of such size that they could only be lifted with the help of their comrades.

But, unfortunately, there are some peculiarities of their storage. For example, if a crystal of alum is left open in dry air, it will gradually lose the water it contains and turn into an inconspicuous gray powder. To protect it from destruction, you can coat it with colorless varnish. Copper sulfate and table salt are more stable and you can safely work with them.

Last year, in the 7th grade, in a chemistry lesson, while studying the topic “Phenomena occurring with substances,” we grew crystals; many people did not succeed in this experiment. This year I told the 7th grade kids how to do this task correctly and this is what they did (see Appendix 2).

Conclusion

All the physical properties due to which crystals are so widely used depend on their structure - their spatial lattice.

Along with solid-state crystals, liquid crystals are currently widely used, and in the near future we will use devices built on photonic crystals.

I selected the most suitable method for growing crystals at home and grew crystals of salt and copper sulfate. As the crystals grew, he made observations and recorded changes.

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. But speaking quite seriously, now, perhaps, it is impossible to name a single discipline, not a single area of science and technology that could do without crystals. Doctors are interested in the environments in which crystallization of kidney stones occurs, and pharmacists are interested in tablets that 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.

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. Crystallography is not a new science. M.V. Lomonosov stands at its origins. 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? For example, artificial diamond is still inferior to natural diamond in quality, including 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 environment, temperature, pressure, and the effects of some other additional conditions. And this is already a whole art, creativity, mastery - the exact sciences will not help here.

The topic “Crystals” is relevant, and if you delve into it and delve deeper, it will be of interest to everyone, it will give answers to many questions, and most importantly - the unlimited use of crystals. Crystals are mysterious in their essence and so extraordinary that in my work I have told only a small part of what is known about crystals and their use at the present time. It may be that the crystalline state of matter is the step that united the inorganic world with the world of living matter. Future latest technologies belongs to crystals and crystalline aggregates!

Based on my research, I came to the following conclusions: conclusions:

Artificially grown crystals are used in a wide variety of fields: medicine, radio engineering, aircraft construction, optics and many others.
The period for obtaining artificial crystals is much shorter than the process of their natural formation. Which makes them more accessible to use.
You can grow crystals at home even in a short time.

Bibliography

Chemistry. Introductory course. 7th grade: educational. Benefit / O.S. Gabrielyan, I.G. Ostroumov, A.K. Akhlebinin. – 6th ed., M.: Bustard, 2011.
Chemistry. 7th grade: workbook for the textbook O.S. Gabrielyan et al. “Chemistry. Introductory course. 7th grade”/ O.S. Gabrielyan, G.A. Shipareva. – 3rd ed., - M.: Bustard, 2011.
Landau L.D., Kitaygorodsky A.I. Physics for everyone, Book 2. Molecules. - M., 1978.
Encyclopedic dictionary of a young chemist. / Comp. V.A. Kritsman, V.V. Stanzo.-M., 1982.
Encyclopedia for children. Volume 4. Geology. / Comp. S.T. Ismailova.-M., 1995.
Internet resources:

http://www.krugosvet.ru – Encyclopedia Around the World.

http://ru.wikipedia.org/ - Wikipedia encyclopedia.

http://www.kristallikov.net/page6.html - how to grow a crystal.

Annex 1.

Observation diary

date	Observations		Photo
date	Salt	Copper sulfate	Salt	Copper kuparos
24.01.14.	Before lowering the seed into the solution. length:5mm width:5mm	We make a loop of wire, hang it and lower it into the solution.
27.01.14.	length:11mm width:7mm	length:12mm width:10mm
30.01.14.	length:20mm width:10mm	length:18mm width:13mm
3.02.14.	Crystal formation has extended beyond the solution boundary	length:25mm width:15mm
6.02.14.	The crystal turned out to be large, but shapeless	length:30mm width:20mm

Appendix 2

Crystals grown by seventh graders

Slide captions:

Applications of crystals
Decorations
Lenses
Prepared the seed

Target
: determine the main areas of application of artificial crystals and test experimentally the possibility of growing crystals of table salt and copper sulfate without the use of special equipment.
Tasks:

Collect material about crystals and their properties.
Conduct experiments on growing crystals of copper sulfate and table salt.
Systematize material about crystals: physical properties of crystals and their applications.
Create a presentation “Crystals and their applications.”
2. Displacement of metals from salt solutions using more active metals.
Passed the solution through a filter
Thank you for your attention
Main applications of artificial crystals
Completed by an 8th grade student
Fetisov Nikolay
Supervisor
Sizochenko
A.I. ,
Physics teacher
Municipal secondary education
Establishment
"Basic general education
School No. 24"
Novokuznetsk, 2014
conclusions
Artificially grown crystals are used in a variety of fields: medicine, radio engineering,
car-plane
structure, optics and many others.
The period for obtaining artificial crystals is much shorter than the process of their natural formation. Which makes them more accessible to use.
You can grow crystals at home even in a short time.
Crystal growing methods
Method
Czochralski
- crucible
method:
melt
substance from which
supposed to crystallize
stones are placed in a fireproof
crucible
made of refractory metal (platinum, rhodium,
iridium
, molybdenum, or tungsten) and heated in
high frequency
inductor.
(Gemstones: rubies)
Clay crucible
Growing crystals at home
Method 1
: Slow cooling of a saturated solution
Preparing a supersaturated solution
Polycrystals
Monocrystals
Crystals grown by seventh graders
Liquid crystals
Crystals
- these are solid
substances,

having natural
external form
regular symmetric polyhedra
, based
on
their internal
structure
Semiconductor diodes, transistors, solar panels
Method 2:
Gradual removal of water from a saturated solution

IN
In this case, the slower the water is removed, the better the result.

You need to leave the vessel
with table solution
salt,
covering it with a sheet of paper, while water
evaporates
slowly, but the dust does not enter the solution
hits.

Crystal
It turned out big, but shapeless - amorphous.

Back forward

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Introduction

We live in a world in which most substances are in a solid state. We use various mechanisms, tools, devices. We live in houses and apartments. We have furniture, household appliances, the most modern means of communication: television, radio, computers, etc. But all these are solid bodies. From a physical point of view, a person is a solid body. So what are solids?

Unlike liquids, solids retain not only volume, but also shape, since the position in space of the particles that make up the body is stable. Due to significant forces of intermolecular interaction, particles cannot move away from each other over significant distances.

In nature, there are often solid bodies that have the shape of regular polyhedra. Such bodies were called crystals. The study of the physical properties of crystals has shown that a geometrically correct shape is not their main feature.

The famous saying of academician A.E. Fersman “Almost the entire world is crystalline. The world is ruled by the crystal and its solid, linear laws” is fully consistent with the undying scientific interest of scientists around the world and all fields of knowledge in this object of research. At the end of the 60s of the last century, a serious scientific breakthrough began in the field of liquid crystals, which gave rise to the “indicator revolution” to replace pointer mechanisms with means of visual display of information. Later, the concept of a biological crystal (DNA, viruses, etc.) entered science, and in the 80s of the twentieth century - a photonic crystal.

What are crystals? What properties do they have? What is a crystal lattice? How do crystals grow? Is it possible to grow a crystal at home? How and where are they currently used? What crystals can be called precious stones? These questions interested us, and we tried to find answers to them, because in the textbook this topic is given only one paragraph and we did not find answers to these questions, or these answers were incomplete. We consider the topic “Crystalline bodies” to be relevant. Thanks to the latest discoveries in the field of solid state physics, or more precisely in the physics of crystalline solids, there has been a huge leap in the development of science and technology, modern communications, computer technology, and spacecraft.

Therefore, we decided to study this problem most fully and comprehensively, set goals and specific tasks.

Goals of work:

To trace the evolution of views on the nature of crystals;
Study the structure and physical properties of crystals, thanks to which they have found such wide application;
Explore the applications of crystals;
Find out why people have long been paying attention to certain crystals and calling them precious, for what properties and qualities.
Growing crystals and monitoring their growth process.

Conduct an analysis of sources on the project topic;
Get acquainted with the ideas of scientists about solid crystals over several centuries;
Consider the features of spatial lattices and their classification;
Study the physical properties of crystals;
Get acquainted with the use of liquid crystals;
Choose a method suitable for growing crystals at home;
Create a multimedia presentation on the topic of the project.

2. Crystals and their physical properties

2. 1. The concept of “crystal”.

The ancient Greeks used the word “krystallos” to mean ice. Water-transparent quartz (rock crystal), which was then mistakenly considered “petrified ice,” was also called. Subsequently, this term was extended to all crystalline bodies.

Crystals are usually called solids that form under natural or laboratory conditions and have the form of polyhedra that resemble the most rigorous geometric structures. The surface of such figures is limited by perfect planes - edges intersecting along straight lines. The intersection points of the edges form the vertices. This definition cannot be called correct and it requires a number of significant amendments, since it does not cover all crystalline formations. Here are a few examples to prove this:

This theory played a major historical role in its time, giving impetus to the emergence of the theory of the lattice structure of crystals. This does not exhaust the merits of Gayuya. For the first time he drew attention to the fact that an observer looking at a crystal from different sides often seems to be repeating the same picture in front of him. This is explained by the fact that such a crystal consists of repeating equal parts. Gayuy was one of the first to grasp the symmetrical structure of many crystalline bodies

The French crystallographer Bravais, being a sailor-meteorologist, became interested in the shapes of snowflakes and began to study in depth the science of crystals. Unlike his predecessors, who attributed a spherical or parallelepipedal shape to elementary particles in crystals, Bravais abandoned any assumptions regarding the mysterious and then inaccessible forms of molecules or atoms. The molecular “building blocks” of Haüy were replaced by Bravais points and their centers of gravity. Having identified the centers of gravity of all bricks in the brickwork, we obtain the spatial lattice already familiar to us.

Having hypothesized the lattice structure of all crystalline bodies in general, Bravais laid the foundation for modern structural crystallography long before experimental studies of crystal structures using X-rays. According to the law of crystallographic symmetry, only symmetry axes of the first, second, third, fourth and sixth orders are possible for crystals. Thus, crystalline figures never have symmetry axes of the fifth order, as well as symmetry axes of order higher than the sixth, since they are impossible in lattices. (See Appendix No. 4)

In 1867, our compatriot, a major military specialist, professor of the artillery school, Academician A.V. Gadolin (1828-1892) was also a great lover and expert on minerals and their crystalline forms. In his classic work “Derivation of all crystallographic systems and their subdivisions from one common beginning“The existence of 32 types of symmetry for finite crystallographic figures was established once and for all. They are the basis for the mathematical derivation of the shapes possible for crystals.

A complete set of symmetry elements for finite crystalline figures (crystalline polyhedra): C, P, L|, L2, L3, L4, C, Li4, L|6.

Having gone through all possible combinations of the listed symmetry elements, we get 32 combinations - 32 types of symmetry (See. Appendix No. 4).

Types of symmetry are divided into three categories (lower, middle and highest) and into seven systems - syngonies. “Syngony” means similar angle in Greek. The name “triclinic” also indicates in Greek three oblique angles (the system of coordinate axes for triclinic crystals is entirely oblique). “Monoclinic” - one oblique angle (in the coordinate axes system there is one oblique angle and two straight angles). The “orhombic” system often reveals the presence of orthorhombic cross-sections in crystals. “Trigonal” - triangular; “tetragonal” - quadrangular; “hexagonal” - hexagonal. These names are also associated with characteristic cross-sections of the crystalline forms. The name “cubic” system comes from the main form - the cube.

2. 4. Single crystals and polycrystals

Crystalline bodies can be single crystals or polycrystals. A single crystal is called a single crystal, having a macroscopic ordered crystal lattice. Single crystals usually have a geometrically regular external shape, but this feature is not mandatory.

Most solids found in nature and produced by technology are a collection of small, chaotically oriented small crystals fused together - crystallites. Such bodies are called polycrystals. Unlike single crystals, polycrystals are isotropic, that is, their properties are the same in all directions.

2.5 Crystal polymorphism

Many substances in the crystalline state can exist in two or more phase varieties (modifications), differing in physical properties. This phenomenon is called polymorphism. Each modification is stable in a certain temperature and pressure range.

The ordered arrangement of atoms or molecules in a crystal is determined by the action of interatomic or intermolecular interaction forces. Thermal movement of atoms and molecules disrupts this ordered structure. At each combination of pressure and temperature, the type of particle arrangement that in these cases is most stable and energetically favorable is realized, i.e., one or another phase state.

Transformations of crystals of the same substance with different types lattices with each other occur in accordance with phase transitions such as melting and evaporation. Each pressure corresponds to a certain temperature at which both types of crystals coexist. When these conditions change, a phase transition occurs. A good example of this phenomenon is carbon. There are three allotropic modifications of carbon found in nature: diamond, graphite and carbyne. (Cm. Appendix No. 5)

Diamond is a crystalline substance with an atomic crystal lattice. Each atom in a diamond crystal is connected by atoms. This is what makes diamond exceptionally hard. Diamond is widely used for processing particularly hard materials: for cutting glass, during drilling operations, for drawing wire, etc. Diamond practically does not conduct electricity, conducts heat poorly. Transparent diamond samples strongly refract light rays and shine beautifully when cut; jewelry (diamonds) are made from such diamonds.

Graphite is opaque, gray in color, and has a metallic luster. In the crystal lattice of graphite, carbon atoms are arranged in layers consisting of six-membered rings. In them, each carbon atom is linked by strong covalent bonds to three neighboring atoms. Due to the fourth valence electron of each layer, a metallic bond is formed. This explains the metallic luster and fairly good electrical and thermal conductivity of graphite. Electrodes for electrochemical and electrometallurgical processes are made from graphite.

Intermolecular forces act between layers in graphite. Therefore, graphite easily exfoliates into flakes. With weak friction of graphite on paper, a gray mark remains on it (“graphite” from the Latin “writing”). Graphite is used to make pencil leads and in technology as a lubricant.

Graphite is refractory and chemically very stable. Fireproof crucibles are made from a mixture of graphite and clay for smelting metals in metallurgy. Graphite is used as a material for heat exchanger pipes in the chemical industry. In nuclear reactors it is used as a neutron moderator.

Carbin became known relatively recently. It was obtained by Soviet scientists, and later discovered in nature. This is black powder. The crystal lattice is built from linear carbon chains. In terms of electrical conductivity, carbyne occupies an intermediate position between diamond (dielectric) and graphite (conductor): carbyne is a semiconductor.

Allotropic modifications of carbon are interconvertible. When heated, diamond gradually turns into graphite. To transform graphite into diamond, very high pressure (of the order of MO" Pa) and high temperature (1500-3000 ° C) are required. Currently, the artificial production of diamonds from graphite is carried out on a production scale.

2. 6 Anisotropy of crystals

The density of particles in the crystal lattice is not the same in different directions. This leads to a dependence of the properties of single crystals on the direction of anisotropy.

Anisotropy is the dependence of the physical properties of a substance on direction. The physical properties of polycrystals do not depend on direction: they are isotropic.

Isotropic independence of the physical properties of matter from direction.

The simplest example of crystal anisotropy is their unequal strength in different directions. This property is clearly manifested when crushing crystalline bodies.

Thermal, electrical and optical properties are also not the same in different directions. The anisotropy of the physical properties of crystals and the correct external shape were explained on the basis of the atomic-molecular theory of the structure of matter.

The thermal conductivity of single crystals is also different in different directions. In graphite, thermal conductivity along the layers is four times greater than normal to the layers: heat is more easily transferred in those planes and directions where the atoms are more densely packed.

Graphite is an example of a crystal with a so-called layered structure; the difference in structure along and across the layers is striking. In other structures, these differences may not be so obvious, but the anisotropy of the properties of the crystal always depends on the symmetry of the structure, on the arrangement of atoms, and on the bonding forces between them.

The anisotropy of the mechanical properties of crystals is especially obvious. Crystals with a layered structure - mica, gypsum, graphite, talc in the direction of the layers are very easily split into thin leaves, but it is impossible to cut or split them in other planes.

Colorless rock salt crystals are transparent, like glass. But they don’t break like glass at all. If you hit the crystal with a knife or hammer, it breaks into cubes with even, smooth, flat edges. This is the phenomenon of cleavage. i.e., the ability to split along even, smooth planes, the so-called cleavage planes. Calcite crystals also have very perfect cleavage: when struck, they always break into so-called rhombohedrons with smooth, flat faces. A rhombohedron is an oblique parallelepiped, or, one might say, a cube extended along one of its diagonals.

Cleavage is a manifestation of the anisotropy of the strength of crystals: the adhesion forces between atoms in some symmetrically located planes are very small, and the crystals split along these planes.

3. Crystals - precious stones.

3. 1 Origin and structure of precious stones.

All precious stones, with rare exceptions, belong to the world of minerals. Let us recall their origin and structure. Minerals can occur in a variety of ways. Some are formed from fiery liquid melts and gases in the bowels of the Earth or from volcanic lavas erupted onto its surface (igneous minerals). Others fall out of aqueous solutions or grow with the help of organisms on (or near) the earth's surface (sedimentary minerals). New minerals are formed by recrystallization of existing minerals under the influence of high pressures and high temperatures in the deep layers of the earth's crust (metamorphic minerals).

The chemical composition of minerals is expressed by the formula. Impurities are not taken into account, even if they cause the appearance color shades, up to a complete change in the color of the mineral. Almost all minerals crystallize in certain forms, that is, they are crystals - bodies of homogeneous composition with a regular arrangement of atoms, ions or molecules in a lattice. The crystals are characterized by strict geometric shapes and are limited by predominantly smooth, flat edges. For the most part, the crystals are small, some even microscopically small; but there are also giant specimens. The internal structure of crystals (spatial lattice) determines their physical properties, including external shape, hardness and ability to split, type of fracture, density and optical phenomena.

In crystallography, all crystals are systematized, distributed into seven syngonies (systems) (See. Appendix No. 6): cubic, tetragonal, hexagonal, trigonal, orthorhombic, monoclinic and triclinic. The differences between them are made by crystallographic axes and the angles at which these axes intersect.

Cubic system (sometimes also called regular): all three axes are the same length and oriented mutually perpendicular. Typical crystal shapes are cube, octahedron (octahedron), rhombic dodecahedron (12-hedron with tetragonal faces), pentagondodecahedron (12-hedron with pentagonal faces), icositetrahedron (24-hedron), hexakisoctahedron (48-hedron).

Tetragonal, or square, system: three axes are mutually perpendicular; two of them have the same length and lie in the same plane, the third (the main axis) is longer or shorter. Typical crystal shapes are square prisms and pyramids, trapezohedron and octagonal pyramids, and bipyramids.

3. 2 Gem or gem.

This group of stones is distinguished by one feature that unites them - special beauty. Gemstone is a concept that does not have a single definition. Only a few stones were called gems. Now their number has increased sharply and continues to increase. For the most part, these are minerals, much less often - mineral aggregates (rocks). TO precious stones Also include some materials of organic origin: amber, coral, pearls. Even fossilized organic remains (fossils) are used as decorations. In terms of their purpose, a number of other jewelry materials are similar to precious stones: wood, bone, glass and metal. The reproduction of natural gems through synthesis, as well as the artificial production of stones that have no analogues in nature, has further expanded the variety of precious stones.

Ornamental stone. It is a collective term that refers to all stones used both as decoration and for the production of stone carvings. Sometimes less valuable or opaque stones are called ornamental. In practice, it is often used simply as a synonym for the term “gemstone”, since there are no convincing grounds for a clear distinction between “jewelry” and “other” stones.

It is customary to distinguish between jewelry (precious) stones used in jewelry and ornamental stones intended for the production of stone-cutting products. ( boxes, ashtrays, etc.) , as well as an intermediate group of jewelry and semi-precious stones.

Jewel. This is a piece of jewelry consisting of one or more precious stones set in precious metal. Sometimes polished precious stones without a setting, as well as jewelry made of precious metals without stones, are also called jewelry.

Gems have been known to man for at least seven thousand years. The first of these were amethyst, rock crystal, amber, garnet, jade, jasper, coral, lapis lazuli, pearl, serpentine, emerald and turquoise. These stones for a long time remained accessible only to representatives of the privileged classes and not only served as decoration, but also symbolized the social status of their owners. Princely regalia, studded with precious stones, testified to the wealth and power of the feudal lords. To this day, in various treasuries and museums we admire the magnificent jewelry of bygone eras.

Nowadays, there are people who wear a gemstone set in gold or platinum to demonstrate their wealth, but more often jewelry serves our own pleasure, bringing joy with its beauty and harmony.

Even today we acquire this or that gem, experiencing some incomprehensible sympathy or inclination towards it. It is not surprising that in earlier, less enlightened times, mysterious powers were attributed to precious stones. Gems served as amulets and talismans, supposedly protecting their owner from hostile forces and bringing him happiness. Some stones protected from evil, others preserved health, served as an antidote, saved from the plague, evoked the mercy of rulers, or contributed to a safe return from a voyage.

Up to early XIX V. precious stones were even used in medicinal purposes. In some cases, it was considered sufficient to have a certain stone, in others it was placed on a sore spot, in others it was crushed into powder and taken orally. Ancient medical books contain “accurate” information about which stone can help with a particular disease. Treatment with precious stones is called lithotherapy. Sometimes it brought success, but this should not be attributed to the stone itself, but to a psychological suggestion that had a beneficial effect on the patient. Failures in treatment were explained by the fact that the stone turned out to be “not real.” In Japan, tablets made from powdered pearls (that is, mainly from calcium carbonate) are sold for medical purposes today.

A direct consequence of the prevailing idea of supernatural powers inherent in precious stones was their connection with astrology: they were “assigned” to the zodiac constellations. This is where “lucky” birthday stones arose, that is, gems that were supposed to be worn by people born under one or another zodiac sign. These stones should always accompany their owners, supposedly protecting them from all kinds of misfortunes. Subsequently, such gems became “lucky” stones of the months. Likewise, there are stones that are associated with the Sun, Moon and our planets solar system. Over time, the “designation” of precious stones has changed several times. More recently, some countries have chosen a precious stone mined on their territory as their state symbol.

In modern religions, precious stones have a specific place. Thus, the breastplate of the Jewish high priest is decorated with four rows of precious stones. Similar stones sparkle on the tiaras and miters of the pope and bishops of the Christian Church, as well as on arks, monstrances, crayfish and icon frames.

But often gems are considered solely as an investment of capital. And indeed, high price precious stones, enclosed in such small form, has proven its stability in all the economic storms of recent decades.

3. 3 Cleavage and fracture

Many minerals crack or split along smooth flat surfaces. This property of minerals is called cleavage and depends on the structure of their crystal lattice and on the adhesion forces between atoms. Cleavage is distinguished between very perfect (euclase), perfect (topaz) and imperfect (garnet). A number of precious and ornamental stones (for example , in quartz) it is completely absent. Separability is the ability of a crystal to split in certain areas along parallel oriented surfaces.

The presence of cleavage must be taken into account when polishing and cutting stones, as well as when inserting them into a frame. Strong mechanical stress can cause splitting (crack) along the cleavage. Often a light blow or excessive pressure is sufficient to determine hardness. (Cm. Appendix No. 7) Thermal stresses arising during the process of jewelry gas-plasma soldering can lead to the formation of cleavage cracks in the stone, and this not only reduces the value of the stone, but also poses the risk that it will eventually split along the cracks that have arisen. Faceting a precious stone with very perfect cleavage (for example, euclase) requires great skill.

Cleavage was used to carefully dissect large stones into pieces or to separate defective areas. The largest gem-quality diamond ever found, “Cullinan” (3106ct), was split along its cleavage into three large pieces and many small pieces in 1908. Now such operations are performed primarily by sawing, which allows better use of the shape of the stone, as well as avoiding unwanted cracks and splits.

The shape of the surface of the fragments into which the mineral breaks up upon impact is called a fracture. It can be conchoidal (similar to the imprint of a shell), uneven, splintered, fibrous, stepped, smooth, earthy, etc. Sometimes a fracture can serve as a diagnostic sign, allowing one to distinguish between minerals that are similar in appearance. Conchoidal fracture is typical, for example, of all varieties of quartz and glass imitation gemstones.

3. 4 Density

Density (formerly called specific gravity) is the ratio of the mass of a substance to the mass of the same volume of water. Therefore, a stone having a density of 2.6 is the same number of times heavier than an equal volume of water.

The density of gemstones ranges from 1 to 7. Stones with a density below 2 seem light to us (amber 1.1), from 2 to 4 - normal weight (quartz 2.65), and above 5 - heavy (cassiterite 7.0). The most expensive gemstones, such as diamond, ruby, and sapphire, have a higher density than the main rock-forming minerals, primarily quartz and feldspar. Due to this, they are deposited earlier in flowing waters. quartz sands and accumulate in so-called placer deposits.

Determining the density of gemstones can greatly assist a collector in identifying them.

Density is determined by two methods (See. Appendix No. 8): hydrostatic weighing method and heavy liquid immersion method. The first of them, although time-consuming, does not require large expenses. As for the second method, it is quite complicated and sometimes expensive, but it allows you to quickly make a reliable comparison of the density of large batches of unfamiliar stones.

The hydrostatic weighing method is based on Archimedes' principle; by immersing an unknown stone in water, its volume is determined, and the density is then calculated using a simple formula: Density of the stone = Mass of the stone: Volume of the stone

Anyone can make hydrostatic scales on their own. It is enough to adapt pharmaceutical lever scales for this. The test object is weighed first in air and then in water; the difference in the obtained values corresponds to the mass of displaced water and thus, in numerical terms, to the volume of the stone.

3. 5 Measures of the mass of precious stones

The carat is a unit of mass that has been used in the trade in precious stones and in jewelry since ancient times. It is possible that the word “carat” itself comes from the local name (kuara) of the African coral tree, the seeds of which were used to weigh gold dust, but it is more likely that it originates from the Greek name (keration) of the carob tree, widespread in the Mediterranean, the fruit which originally served as “weights” when weighing precious stones (the mass of one such weight on average is approximately equal to a carat). In 1907, the International Committee of Weights and Measures at a conference in Paris introduced a metric carat equal to 200 mg, or 0.2 g. Before that, the weight of the carat adopted in the largest centers of the world trade in precious stones varied somewhat. Hence the discrepancies in the mass of historical diamonds found in the literature. The abbreviation for carat is carat. Fractions of carats are expressed as simple (for example, 1/16 ct) or decimal (accurate to the second decimal place, for example 1.25 ct) fractions. When weighing the smallest diamonds, a unit of mass is also used, called a “point” and equal to 0.01 carats. The figure placed here shows the exact dimensions of modern-cut diamonds and their corresponding carat weights in life-size; it shows how the diameter of the diamond and its mass relate. Of course, for stones that have a different density and other cut shapes, these ratios will be different. The carat as a unit of weight of precious stones should not be confused with the carat as a measure of the purity (fineness) of gold used in jewelry. In this second case, the carat serves not as a unit of mass, but as a measure of the quality of the gold alloy. The higher the number of carats, the higher the content of pure gold in the jewelry, and its weight can be anything.

A gram is a unit of mass used in the gemstone trade for less expensive stones, and especially for unprocessed stone-colored raw materials (for example, the quartz group).

Gran [from lat. granum- grain (of wheat)] - a measure of the mass of pearls. Corresponds to 0.05 g, that is, 0.25 ct. Nowadays granite is increasingly being replaced by carat. The Japanese mass measure “momma” (= 3.75 g = 18.75 ct), previously used in the pearl trade, is now practically not used in European trade.

Price. In the gem trade, the price is usually quoted per carat. To calculate the total cost of a stone, you need to multiply the price and its weight in carats. When selling a stone to the end consumer, the full price is usually quoted. The cost of one carat increases progressively with increasing size and weight of stones.

4. Optical properties of gemstones

Among the physical properties of precious stones, optical properties play a dominant role, determining their color and brilliance, sparkle (“fire”) and luminescence, asterism, iridescence and other light effects. When testing and identifying gemstones, optical phenomena are also becoming increasingly important.

Color is the first thing that catches your eye when looking at any gemstone. However, for most stones, their color cannot serve as a diagnostic sign, since many of them are colored the same, and some appear in several color guises.

The cause of different colors is light, that is, electromagnetic vibrations lying in a certain wavelength range. The human eye perceives only waves in the so-called optical range - from approximately 400 to 700 nm. This region of visible light is divided into 7 main parts, each of which corresponds to a specific color of the spectrum: red, orange, yellow, green, blue, indigo, violet. When all spectral colors are mixed, we get White color. If, however, any wavelength range is absorbed (“absorbed”), a certain color, no longer white, appears from the mixture of other colors. A stone that transmits all wavelengths of the optical range appears colorless; if, on the contrary, all the light is absorbed, then the stone acquires the darkest visible color - black. When light is partially absorbed across the entire visible wavelength range, the stone appears cloudy white or gray. But if, on the contrary, only very specific wavelengths are absorbed, then the stone acquires a color corresponding to the mixing of the remaining unabsorbed parts of the white light spectrum. The main carriers of color - chromophores that determine the color of precious stones - are ions heavy metals: iron, cobalt, nickel, manganese, copper, chromium, vanadium and titanium, capable of absorbing certain wavelengths in the visible region.

The color of zircon and some other minerals is caused not by chromophore ions, but by deformations of the crystal lattice, more precisely, the appearance of radiation defects in it under the influence of radioactive radiation, which causes selective absorption of light.

The absorption of light and thus the color of the crystal is also influenced by the length of the path traversed by the light rays in it. Accordingly, when grinding, it is necessary to strive to use this circumstance to the maximum benefit for the stone. Light-colored stones are polished thicker, and when cutting, facets are applied in such a way as to lengthen the path of rays through the stone, that is, to enhance absorption. Stones that are too dark, on the contrary, should be polished thinner to lighten them somewhat. For example, a dark red almandine garnet, when polished into a cabochon, is drilled from the underside to make it hollow.

The color of gemstones also depends on lighting, since the spectra of artificial (electric) and daylight (sun) light are different. There are stones whose color is adversely affected by artificial light (sapphire), and those that only benefit from evening (artificial) light, enhancing their radiance (ruby, emerald). But the change in color is most pronounced in alexandrite: during the day it looks green, in the evening it looks red.

4. 2 Light refraction

We have seen more than once that a stick, not completely immersed in water at an acute angle, seems to “break” at the water surface. The lower part of the stick, located in the water, acquires a different slope than the upper part, located in the air. This occurs due to the refraction of light, which always appears when a light beam passes from one medium to another, that is, at the boundary of two substances, if the beam is directed obliquely to the surface of their interface.

The amount of light refraction of all crystals of precious stones of the same mineral type is constant (sometimes it fluctuates slightly, but within a very narrow interval). Therefore, the numerical expression of this value - the refractive index (often called simply refraction or light refraction) - is used to diagnose gemstones. The refractive index is defined as the ratio of the speed of light in air and in a crystal. The fact is that the deflection of a light beam in a crystal is caused precisely by a decrease in the speed of propagation of this beam in an optically denser medium.

In diamond, light travels 2.4 times slower than in air. The refractive indices of gemstones are in the range of 1.2-2.6. Depending on the color and origin of the gemstone, its refraction may vary slightly. Birefringent stones have two or even three refractive indices. In practice, refractive indices are measured using a refractometer. Their values are directly read from the instrument scale. .

Without great technical difficulties and costs, it is possible to measure light refraction using the immersion method - immersing a stone in a liquid with a known refractive index and observing the interfaces. How light and sharp the contours of the stone or edges between facets appear, as well as the apparent width of the interfaces, can fairly accurately estimate the refractive index of a gemstone.

4.3 Variance

When passing through a crystal, white light not only undergoes refraction, but is also decomposed into spectral colors, since the refractive indices of crystalline substances depend (and to varying degrees) on the wavelength of the incident light. And since the individual colors of the white light spectrum correspond to different wavelengths, they are refracted differently, as shown in the figure. Let's say, for a diamond, the refractive index for red rays (wavelength 687 nm) is 2.407, for yellow (wavelength 589 nm) - 2.417, for green (wavelength 527 nm) - 2.427 and for violet (wavelength 397 nm) - 2.465 . The phenomenon of decomposition of white light by a crystal into all the colors of the rainbow is called dispersion.

Dispersion is clearly visible only in colorless stones. Natural and synthetic stones with high dispersion (e.g. fabulite, rutile, sphalerite, titanite, zircon) are used V in jewelry as diamond substitutes. The difference in refractive indices for the wavelengths of the red and violet parts of the spectrum is usually taken as a numerical measure of the dispersion of gemstones.

4. 4 Surface optical effects: light figures and color tints

Many jewelry stones exhibit light patterns in the form of stripes of light oriented in a certain way, as well as surface color tints. Neither one nor the other depends either on the stone’s own color or the presence of impurity elements, or on its chemical composition. The reasons for their appearance lie in the phenomena of reflection, interference and diffraction of light waves.

Effect " cat eye” is inherent in stones that are aggregates of parallel fused fibrous or needle-shaped individuals or containing thin parallel-oriented hollow channels. The effect occurs due to the reflection of light on such parallel accretion (or channels) and consists in the fact that when the stone is turned, a narrow light stripe runs across it, evoking the luminous slit-like pupil of a cat. The greatest impression of this effect is achieved if the stone is polished in the form of a cabochon, and in such a way that flat base The cabochon is located parallel to the fibrous structure of the stone. The chrysoberyl cat's eye is considered the most valuable and is simply called the cat's eye. But a similar effect occurs in many jewelry stones. The most famous are quartz cat's, falcon's and tiger's eyes. All other varieties of cat's eye, except chrysoberyl, require a more precise mineralogical definition (“quartz”, etc.).

Asterism (from lat. astrum- constellation) - the appearance on the surface of a stone of light figures in the form of light stripes intersecting at one point and reminiscent of star rays; the number of these rays and the angle of their intersection are determined by the symmetry of the crystals. In its nature, it is similar to the cat's eye effect, with the only difference being that the reflective inclusions - thin fibers, needles or tubules - have different orientations in different areas. The six-pointed stars of the ruby and sapphire cabochons make a great impression. . Other stones also have four- and, in isolated cases, twelve-rayed stars. Rose quartz, ground into a ball shape, has rays running in circles across the entire surface. If the regular arrangement of needle-shaped inclusions turns out to be partially disrupted, then underdeveloped stars appear, having the appearance of circular scales with division lines or bright light points - “light knots”. Star-shaped stones are called asteria. Asterism is also created in synthetic jewelry stones.

Adulariscence is the bluish-white shimmering glow of moonstone, a precious variety of adularia (hence the name of the effect). As the moonstone cabochon moves, this glow, or shimmer, glides across its surface. The effect is explained by the interference of light on thin parallel plates of orthoclase and albite (cryptoperthite), from which the moonstone is built.

Adventurescence is a variegated color play of brilliant, sparkling reflections of light from scaly inclusions on a mostly opaque background (in opaque stones). In aventurine feldspar, or sunstone, the shiny flakes belong to hematite or goethite, in aventurine quartz they are flakes of chromium-containing mica (fuchsite) or hematite, in artificial aventurine glass they are copper shavings.

Iridization (from lat. iris- rainbow) - an iridescent color play of some jewelry stones, the result of the decomposition of white color, refracted at small breaks and cracks in the stone, into spectral colors. In rock crystal, this effect is enhanced or even artificially caused by creating cracks in the stone, since iridescence increases its value.

5. Liquid crystals

5.1 The concept of “liquid crystal”

More and more often we began to encounter the term “liquid crystals”. We all often communicate with them, and they play an important role in our lives. Many modern devices and devices work on them. These include watches, thermometers, displays, monitors and other devices. What kind of substances are these with such a paradoxical name “liquid crystals” and why is there such significant interest in them? In our time, science has become a productive force, and therefore, as a rule, increased scientific interest in a particular phenomenon or object means that this phenomenon or object is of interest for material production. In this regard, liquid crystals are no exception. Interest in them is primarily due to the possibilities of their effective use in a number of industries. The introduction of liquid crystals means cost-effectiveness, simplicity, and convenience.

5. 2. Classification of liquid crystals and their physical properties

At that time, the existence of liquid crystals seemed like some kind of curiosity, and no one could imagine that almost a hundred years later they would have a great future in technical applications. Therefore, after some interest in liquid crystals immediately after their discovery, they were practically forgotten after some time.

The contradictory properties of liquid crystals seemed very dubious to many authorities, but also that the properties of various liquid crystalline substances (compounds that had a liquid crystalline phase) turned out to be significantly different. Thus, some liquid crystals had very high viscosity, while others had low viscosity. Some liquid crystals showed a sharp change in color with a change in temperature, so that their color ran through all the tones of the rainbow, while other liquid crystals did not show such a sharp change in color. Appearance samples of various liquid crystals, when viewed under a microscope, turned out to be completely different. In one case, formations similar to threads could be visible in the field of a polarizing microscope, in another, images similar to mountain relief were observed, and in the third, a pattern resembled fingerprints.

The credit for creating the foundations of the modern classification of liquid crystals belongs to the French scientist J. Friedel. In the twenties, Friedel proposed dividing all liquid crystals into three large groups (See. Appendix No. 9).

Friedel called one group of liquid crystals nematic, the other smectic. He also suggested general term for liquid crystals - “mesomorphic phase”. This term comes from the Greek word “mesos” (intermediate), and by introducing it, Friedel wanted to emphasize that liquid crystals occupy an intermediate position between true crystals and liquids, both in temperature and in their physical properties. Nematic liquid crystals in Friedel's classification included the cholesteric liquid crystals already mentioned above as a subclass.

The most “crystalline” among liquid crystals are smematic. Smatic crystals are characterized by two-dimensional order. The molecules are placed so that their axes are parallel. Moreover, they “understand” the command “equal” and are placed in orderly rows, packed on smatic planes, and in ranks on nematic planes. Smectic liquid crystals have much of what will be discussed below, and something special is long-term memory. Having recorded, for example, an image on such a crystal, you can then admire the “work” for a long time. However, this feature of smetic crystals is not very convenient for the reproducing elements of display devices, televisions and displays. However, they find application in industry, for example in pressure indicators.

The order of nematic media is lower than that of smematic media. Molecules are allowed to shift relative to long axes, so ordering becomes “one-sided”, and the reaction to external influence relatively fast, memory short. Smectic planes are absent, but nematic ones are preserved. The term “cholesteric liquid crystals” is not accidental, since the most characteristic and in practice the most used crystal of this class is cholesterol. Cholesterol and analogue molecules are located in nematic planes. The peculiarity of molecules of the cholesteric type is that with a sufficiently strong lateral attraction, their vertices repel. Cholesterol is an accessible and fairly cheap material, for which any slaughterhouse is rich in raw materials. Very complex liquid crystal structures form solutions of soap in water. Here you can get layered, disk and even spherical structures.

In sufficiently large volumes of crystalline liquid, domains are formed whose physical properties are similar to crystals. However, in general it exhibits properties similar to ordinary liquids. The domain structure of liquid crystals is formed for the same reasons and laws as in ferroelectrics and ferromagnets. The situation changes dramatically in films whose thickness is comparable to the radius of interaction between liquid molecules and the plates forming the layer. It is the interaction of the liquid crystal and the formative elements that creates the easily controllable device that is so actively integrated into modern electronic technology.

6. Applications of liquid crystals

Flat panel TFT displays have two significant disadvantages compared to conventional CRT monitors:

(1) If you look at the TFT display from the side, at some angle, you can clearly notice a significant loss of brightness and a characteristic change in the colors of the display. Older flat panel displays generally have a viewing angle of 90°, or 45° on each side. If only one person is looking at the screen, there is no problem. But as soon as a second user appears, for example, your friend to whom you want to show something on the screen, or the second player in computer game- you won’t have to wait long for comments about the poor quality of the display.

The rapid changes in screen image that often occur when playing videos or playing games require performance levels that are too much for LCD technologies used today. A significant pixel response time leads to distortions and the appearance of characteristic stripes in the image.

Manufacturers of flat panel displays prefer not to rest on the laurels of their success, but to continue research. Recently, the first models made using new advanced technologies were released onto the market. The main technologies are TN+Film, IPS (or "Super-TFT") and MVA, each of which is described in this article

From a technical point of view, the TN+Film solution is the easiest to implement. Flat panel display manufacturers use relatively old technology TFT ( T wisted N ematic). A special film is applied to the top surface of the panel, and the horizontal viewing angle increases from 90° to 140°. However, poor contrast and slow response times remain unchanged. The TN+Film method is not the best solution, but it is undoubtedly the cheapest method because it produces the highest production yield (about the same as conventional LCD displays).

6. 3 IPS (In-Plane Switching or Super-TFT) (See Appendix No. 12)

IPS or "In-Plane Switching" was originally developed by Hitachi, but companies such as NEC and Nokia are now also using the technology.

The difference compared to conventional LCDs (TN or TN+Film) is that the liquid crystal molecules are aligned parallel to the substrate.

This technology allows you to achieve excellent viewing angles - up to 170°, approximately the same as CRT monitors. However, this technology also has a disadvantage: due to the parallel alignment of the liquid crystals, the electrodes may not fit on glass surfaces, as is the case with LCD displays with twisted crystals. Instead, they should be designed as a ridge on the bottom glass surface. This eventually leads to a decrease in contrast and then a more intense backlight is required to increase the brightness to the required level. Response time and contrast can hardly be improved compared to conventional TFT displays.

MVA technology allows you to achieve viewing angles of up to 160° - a fairly good indicator - as well as high contrast values and short pixel response time.

Letter M in MVA it means "Multi-domains" - "multi-domain". A domain is a collection of molecules. In Fig. Figure 3 shows several domains that are formed using electrodes. Fujitsu currently produces displays in which each color cell contains up to four domains.

VA stands for "Vertical Alignment" - a term that is a bit of a misnomer because the liquid crystal molecules (in a static state) are not completely vertically aligned due to the presence of lumpy electrodes. When voltage is applied and an electric field is generated, the crystals are aligned horizontally, and light from the backlight can pass through different layers. MVA technology achieves faster response times than IPS and TN+Film technologies, which is important for video playback and gaming. Contrast is usually better, but may vary somewhat depending on the viewing angle.

6.5 Comparison various technologies improved viewing angle

MVA technology provides improved response time and good values viewing angle

Solution TN+Film does not provide significant improvements in pixel response time. Moreover, such systems are inexpensive, allow for a sufficient production level and increase the viewing angle to acceptable values. The market share of such displays should decrease over time.

IPS have already gained significant market share as they are produced by several companies such as Hitachi and NEC that support the technology. The decisive factors for the success of these displays are high value viewing angle (up to 170°) and acceptable reaction time.

From a technical point of view, technology MVA is the best solution. Viewing angles up to 160° are almost as good as CRT monitors. The response time of approximately 20 ms is also suitable for video playback. The market share of such displays is still small, although it is gradually growing.

7. Technology for growing crystals at home (See. Appendix No. 14)

Crystals were grown mainly by gradually cooling a saturated solution, since this allows for the growth of large crystals of the correct shape in a shorter time.

We made frames from wire in the shape of letters (or some other shapes). Carefully wrapped the wire frames with woolen threads. We made a seed. (To wool thread attached salt crystals. Then they were immersed in a solution (so that the frames did not touch the bottom and walls of the jar, or each other), where the formation and growth of crystals on the surface of the thread fibers occurred. Preparation of the solution. A 500 ml glass was filled with water and heated on a grid to 35-40°C. Then the taken substance, for example copper sulfate, was gradually poured in. (based on 1 liter of water 100 g of substance). The solution must be stirred all the time with a glass rod with a rubber tip. When all the salt had dissolved, more was added, maintaining the same temperature all the time. If the copper sulfate stopped dissolving, then the dissolution was stopped.

The saturated hot solution was quickly filtered through cotton wool into a second similar glass, and the frame with the seed was immersed in it.

We used this technology to grow four crystals: copper sulfate, iron sulfate, potassium alum and table salt. We watched the growth every day. After studying the literature, we learned that growing a single crystal is very difficult. To do this, you need to strictly observe all the conditions of the technology, starting with special dishes, cleanliness of the solution and ending with compliance with the strictest temperature conditions. But we were doing experimental work in winter; the solution cooled very quickly, so it was not possible to maintain a constant temperature. We also had to periodically heat the contents and add more substances to the solution. All these deviations from technology led to the fact that the crystals grew fused, i.e., we got polycrystals with pronounced flat edges of individual crystals.

8. Study of the physical properties of the grown crystal

8. 1 Observations on the growth of a copper sulfate crystal (See. Appendix No. 15 )

Without changing the position of the seed, we periodically measured the sizes of some faces and noticed the following: the faces change their sizes - they grow, but their shape remains unchanged, the angles between the corresponding faces also remain constant. But perhaps this pattern is characteristic only of this crystal? So we grew two different crystals of copper sulfate, compared the shapes of the faces and measured their angles. It turned out that this pattern is also true for another crystal. This gives us the right to say that in different crystals of the same substance, the shape of the faces, their mutual distances, and their number can change, but the angles remain constant.

8. 2 Study of thermal conductivity of crystals (See. Appendix No. 16)

Not all physical properties can be examined at home. We tried to study the largest crystals for thermal conductivity, i.e. how they conduct heat. We applied a drop of paraffin to different faces of the crystals and let it harden. Then they touched these edges with a well-heated knitting needle and observed the shape of the melting droplet of paraffin. In some cases, the shape was round, and in others elongated, which means that in the first case, heat spread in all directions equally, and in the second, heat spread more slowly in some directions, and faster in others, and the shape of the thawed patch was no longer round . Thermal conductivity is different in different directions. It is greater along the layers than normal to the layers: heat is more easily transferred in those planes and directions where the atoms are more densely packed.

9. Application of crystals in science and technology

The applications of crystals in science and technology are so numerous and varied that they are difficult to list. 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-blue sapphire are siblings, they are generally the same mineral - corundum, aluminum oxide A12O3. The difference in color arose due to very small impurities in aluminum oxide: an insignificant addition of chromium turns colorless corundum into a blood-red ruby, titanium oxide into sapphire. There are corundums of other colors. They also have a very modest, nondescript brother: brown, opaque, fine corundum - emery used to clean metal, from which sandpaper is made. 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 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 with enormous power. It easily burns through sheet metal, welds metal wires, burns through metal pipes, and drills the thinnest holes in hard alloys and diamond. These functions are performed by a solid laser using ruby, garnet and neodite. In eye surgery, neodyne lasers and ruby lasers are most often used. Ground-based short-range systems often use gallium arsenide injection lasers.

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, that is, 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, mainly artificially synthesized substances: blue salt, barium titanate, potassium and ammonium dihydrogen phosphates (KDP and ADP) and many others.

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. Piezoelectric plates measure, for example, the pressure in the barrel of an artillery gun when fired, the pressure at the moment of a bomb explosion, the instantaneous pressure in engine cylinders when hot gases explode in them.

The polycrystalline material Polaroid has also found its use in technology.

Crystals played an important role in many technical innovations of the 20th century. Some crystals generate an electrical charge when deformed. Their first significant application was the manufacture of radio frequency oscillators stabilized by quartz crystals. By forcing a quartz plate to vibrate in the electric field of a radio frequency oscillatory circuit, the reception frequency can thereby be stabilized.

Semiconductor devices, which revolutionized electronics, are made from crystalline substances, mainly silicon and germanium. In this case, alloying impurities that are introduced into the crystal lattice play an important role. 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. Crystals are also used in some masers to amplify microwave waves and in lasers to amplify light waves. Crystals with piezoelectric properties are used in radio receivers and transmitters, in pickup heads and in sonar. Some crystals modulate light beams, while others generate light under the influence of an applied voltage. The list of uses for crystals is already quite long and is constantly growing.

10. Conclusions of the design and research work:

1. All the physical properties due to which crystals are so widely used depend on their structure - their spatial lattice.

2. Precious stones belong to the world of minerals, that is, they are grown by nature in the depths of the Earth from solutions, melts or by recrystallization. The chemical composition of such crystals is expressed by the formula. Man's attitude towards precious stones has undergone changes over many centuries: from deification and use in medicine to demonstrating one's wealth or delivering aesthetic pleasure from the beauty and harmony of a stone.

3. Along with solid-state crystals, liquid crystals are currently widely used, and in the near future we will use devices built on photonic crystals.

4. We selected the most suitable method for growing crystals at home and grew crystals of copper and iron sulfate, as well as crystals of potassium alum. As the crystals grew, observations were made.

11. Conclusion

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 diversity 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. 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. Now researchers have studied its structure quite well and are learning to control the properties of 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. 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. Doctors are interested in the environments in which crystallization of kidney stones occurs, and pharmacists are interested in tablets that 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. Crystallography is not a new science. M.V. Lomonosov stands at its origins. But growing artificial crystals is a later matter. 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, mastery - the exact sciences will not help here.

The topic “Crystals” is relevant, and if you delve into it and delve deeper, it will be of interest to everyone, it will give answers to many questions, and most importantly - the unlimited use of crystals. Crystals are mysterious in their essence and so extraordinary that in our work we have told only a small part of what is known about crystals and their use at the present time. It may be that the crystalline state of matter is the step that united the inorganic world with the world of living matter. The future of the latest technologies belongs to crystals and crystalline aggregates!

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6. Kornilov V.I., Solodova Yu.P. Jewelry stones. M.: Nedra, 1983.

7. Kosobukin V.A. Photonic crystals // Window to the world (electronic version of the magazine). 2002.

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