XIII Международная студенческая научная конференция Студенческий научный форум - 2021

Glasses are supercooled liquids that did not manage to react to crystalline state upon cooling. Transparency, ability to be painted in any color, high chemical resistance, high strength and hardness, electrical insulation and many other valuable qualities make glass an indispensable building material.

It has not yet been established reliably how and where glass was first obtained. For a long time, primacy in the discovery of glassmaking was given to Egypt, in which glazed faience tiles of the inner cladding of the Zosser’s pyramid (mid III millennium BC) were considered to be undoubted evidence; to an even earlier period (the first dynasty of the pharaohs) are finds of the faience ornaments, that is, glass existed in Egypt already 5 thousand years ago. Egyptian glassmakers melted glass on open hearths in clay bowls. Sintered pieces were thrown hot in the water, where they cracked and these fragments, the so-called frits, were ground into dust by millstones and melted again.

Currently, materials have been developed for an extremely wide, truly - universal range of applications, which are also used initially (for example, transparency, reflectivity, resistance to aggressive environments, beauty and many others) and previously not characteristic of glass - its synthesized qualities (for example, heat resistance strength, bioactivity, controlled electrical conductivity, etc.). Various types of glasses are used in all spheres of human activity: from construction, visual arts, optics, medicine - to measuring equipment, high technology and astronautics, aviation and military equipment.

Modern glass production includes three stages: preparation of raw materials, glassmaking (100-1600 ° C), molding products.

The chemical composition of ordinary window glass is as follows:

SiO2 71-72% (silica - quartz sand, basic oxide)

Na2O 5-7%, (chalk, marble, limestone, dolomite, magnesite)

CaO 5-7%, (chalk, marble, limestone, dolomite, magnesite)

MgO 3-4%, (chalk, marble, limestone, dolomite, magnesite)

Al2O3 2-3% (alumina - feldspars or kaolin)

Fe2O3 <0.1% - give the glass a bottle color.

All these components regulate such properties of glass as: refractoriness, chemical resistance, coefficient of thermal expansion.

In addition, clarifiers, bleaches, mufflers are introduced into the raw material mass (they make the glass opaque). Dyes for glass - compounds of cobalt (blue), chromium (green), manganese (purple), iron (brown), etc.

Before melting the glass, the raw materials are crushed, thoroughly mixed, briquetted and served in a glass melting furnace. Glassmaking consists of three stages: silicate formation (melt), glass formation (air removal) and a student (cooling to molding temperature). The molding method depends on the type of product. To obtain building glass the hood, rolling and pressing are used.

Glass possesses the following properties:

The average density of glass depends on the chemical composition and is about 2400-2600 kg / m3.

Porosity and water absorption are practically zero.

Tensile strength is 30-60 MPa. In the absence of microdefects, the theoretical tensile strength can reach 10-12 thousand MPa. Glass scratches strongly reduce its strength.

The compressive strength of glass is 900-1000 MPa, like steel and cast iron.

Fragility is the main disadvantage of glass. Its homogeneity contributes to the smooth development of cracks.

The hardness of the glass is 5-7 on the Mohs scale.

Optical properties:

- light transmission (transparency) - 88-92%, do not pass through only ultraviolet and infrared rays;

- light refraction n = 1.5-1.52 determines the strength of reflected light and the light transmission of glass at different angles of incidence of light.

Thermal conductivity - does not depend on the composition of the glass and is 0.6-0.8 (W / m · K), which is almost 10 times lower than that of similar crystalline minerals.

The coefficient of linear thermal expansion (CTE) is small, but with sharp uneven heating, the voltage in the glass can reach values ​​that lead to destruction. This explains the low temperature resistance.

The soundproofing ability of the glass is quite high. Glass with a thickness of 1 cm by this indicator is equal to a half-brick wall (12 cm).

Let us consider the main types of glass:

Flat glass

Sheet window glass is produced in six grades with a thickness of 2; 2.5; 3; 4; 5; and 6 mm.

The width of the sheets is 250-1600 mm, the length is up to 2200 mm. The weight of 1 m2 of glass is 2-5 kg. Light transmission is not less than 87%. Defects in window glass include gas bubbles, swirls and banding (surface roughness).

Showcase glass - sheet glass with a thickness of 6-10 mm and sizes up to 3500x6000. It is released polished. Light-diffusing glass transmits light, but does not give through visibility. It can be matte or patterned.

Uviol glass - transmits a large proportion of ultraviolet rays (45-75%). Get it from raw materials with a minimum amount of impurities of iron, chromium and titanium oxides. This glass is used in medical institutions and greenhouses, for the manufacture of lighting devices.

Special sheet glass (functional glass) not only transmits light, but also performs the functions of thermal insulation, sound insulation, protection, creating a decorative effect.

Thermal insulating glasses, thanks to a special coating on the inside of the glass, reduce the amount of heat loss through the glass by reflecting the infrared portion of the spectrum back inside the premises.

Heat-shielding (sun-protection) glasses reflect part of the radiant energy, not letting it into the room due to the fact that a thin metal layer acting like a mirror is applied to the glass surface or a layer of metal oxides is created on the glass surface to reflect light and give the glass gray, greenish or bronze tint. shade.

Safety glasses have enhanced strength properties. Such properties can be ensured by special heat treatment, while bending strength is increased by 5-8 times, and impact strength by 4-6 times. Upon destruction, such glass breaks up into small fragments.

Glass can be hardened by reinforcing by pressing a clean mesh of chrome-plated steel wire into the glass melt, or by laminating (triplex), when a polymer film is pressed into the thickness of the glass, which absorbs the energy of crack propagation upon impact. Triplex is a bulletproof material.

Finishing glass

The combination of the above properties allows you to get high-quality finishing materials from glass.

Sheet decorative glass is widely used in the construction of public buildings.

Especially popular are metallic mirrored glasses of various shades (golden, blue, gray). This technique has been repeatedly used in the construction of buildings in the USA, Canada, Moscow.

Stemalits are sheets of glass, coated on the inside with ceramic paint, followed by heat treatment. Stemalite has over 25 colors. It is used for decoration of buildings.

Glass Tile

Glass tiles can be enameled (due to the application of enamel on it, followed by heat treatment), carpet mosaic (20x20, 25x25 mm), obtained by rolling from colored damped glass and sticker on paper.

Smalts are pieces of colored stained glass of irregular shape up to 20 mm in size, obtained by grinding larger tiles. Used for the manufacture of art mosaic panels

Glassware:

Double-glazed windows are obtained from two (single) or three (double) sheets of glass hermetically connected to each other. Between the sheets of glass there is a layer of dry air or inert gas. The joining of sheets in a double-glazed window can be done by gluing, soldering or welding. Double-glazed windows have low thermal conductivity and sound permeability. They are used for glazing windows and any other light openings (see plastic windows).

Glass blocks are used when it is necessary to obtain a translucent structure with good heat and sound insulation characteristics. They are made on press machines that form the halves of the blocks and weld them. When cooling in blocks, vacuum is formed that improves insulating qualities.

The sizes of glass blocks are from 200x400 to 400x400 with 100 mm. thickness. Blocks can be colorless and colored, thermal conductivity is 2 times lower than that of brick. In addition, glass blocks are two-chamber and light-directional.

Fiberglass is box and T-section. These are long-sized profiled elements up to 5 m. It is used for constructing translucent fences.

Glass pipes due to their high chemical resistance and transparency compete with metal ones. Due to the smoothness, the throughput of such pipes is higher. They are used in medicine, food and chemical industries.

Glass fiber is obtained by forcing a glass melt through the thinnest dies (holes), followed by drawing. The fiber diameter is 3-100 microns, length up to 20 km. Fiberglass is used for the manufacture of fiberglass and fiberglass used for reinforcement in the production of fiberglass or the basis for rolled roofing materials.

Foam glass is an effective heat-insulating material. It is obtained from expanded glass when it is in the molten state. In hardened form, it resembles volcanic pumice. On an industrial scale, it is produced in the form of blocks and in the form of granules.

Sitalls and slag metals:

Sittals are glass-crystalline materials obtained by directed partial crystallization of glasses. The structure of the glass is reminiscent of concrete, where the aggregate is crystals and the binder is glass. The proportion of glass phase in the glass is 20-40%.

The raw materials for sitalls are the same as for glass, but modifiers for partial crystallization are additionally introduced. Cementals are characterized by high strength (Rszh = 300-600MPa) and durability where they can compete with granite.

Sitalls are used in the chemical industry and hydraulic engineering.

Stone casting

Variety of building materials can be obtained from mining and metallurgical slag by melting (1400-1500 ° C) and casting.

The raw materials are igneous (basalt, diabase), sedimentary (dolomite, limestone, sand) rocks and slags.

Stone casting properties are superior to natural stone materials.

The density of stone casting is 2700-3000 kg / m3; porosity - not more than 1-2%, which ensures almost zero water absorption and the highest frost resistance.

The compressive strength is 200-250 MPa, the hardness is 6-7 on the Mohs scale. Stone casting is characterized by high chemical resistance.

Stone casting is used for cladding structures operating in aggressive environments, subjected to repeated freezing and thawing, intensive abrasion. The main types of stone casting are facing tiles, paving stones for paving roads, grinding bodies and claddings for mills, pipes. Dielectric properties of stone casting are used for the production of insulators.

Today, glass has become an integral part of our lives. To see this, just look around. Glass is utensils, building material, design elements. Glass is an indispensable companion of new ideas in instrumentation and electrical engineering, medicine and the furniture industry, in transport and in everyday life.

Bibliography:

https://infourok.ru/prezentaciya-na-temu-stroitelnie-materiali-iz-stekla-2816070.html

https://works.doklad.ru/view/x0VBnZEpig8.html

https://novate.ru/blogs/231215/34285/

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