The concept of glass and the classification of glass products. Classification of glasses according to technical purpose According to the properties of glass, they are classified into
According to the definition of the Commission for Terminology of the Academy of Sciences of the USSR (1932), “glass is all amorphous bodies obtained by supercooling the melt, regardless of their composition and the temperature range of solidification, and possessing, as a result of a gradual increase in viscosity, the mechanical properties of solid bodies, and the process of transition from a liquid state to a glassy must be reversible.
It follows from the definition that substances belonging to different classes of chemical compounds can be in the glassy state.
Organic glasses are organic polymers - polyacrylates, polycarbonates, polystyrene, copolymers of vinyl chloride with methyl methacrylate - in a glassy state. Glasses based on polymethyl methacrylate have found the greatest practical application. In terms of technology, hardening mechanism, and structure, organic glasses differ significantly from inorganic glasses and constitute a special object of study.
The centuries-old history of glassmaking is associated with the manufacture of silicate glasses based on the Na 2 O-CaO-SiO 2 system. Only in the second half of the XX century. it has been shown that soda calcium silicate glasses constitute a small part of the limitless world of inorganic glasses.
According to the type of inorganic compounds, the following classes of glasses are distinguished: elemental, halide, chalcogenide, oxide, metal, sulfate, nitrate, carbonate, etc.
Elementary glasses with are able to form only a small number of elements - sulfur, selenium, arsenic, phosphorus, carbon.
Glassy - sulfur and selenium, can be obtained by rapid supercooling of the melt; arsenic - by sublimation in vacuum; phosphorus - when heated to 250°C under a pressure of more than 100 MPa; carbon-as a result of long-term pyrolysis of organic resins. Industrial value finds glassy carbon, which has unique properties that surpass the properties of crystalline modifications of carbon: it is able to remain in a solid state up to 3700 ° C, has a low density of the order of 1500 kg / m 3, has high mechanical strength, electrical conductivity, and chemical resistance.
halide glasses are obtained on the basis of the glass-forming component BeF 2 . Multicomponent compositions of fluoroberyllate glasses also contain aluminum, calcium, magnesium, strontium, and barium fluorides. Fluoroberyllate glasses find practical application due to their high resistance to hard radiation, including X-rays, and aggressive media such as fluorine and hydrogen fluoride.
Chalcogenide glasses obtained in oxygen-free systems such as As-J (where Z-S, Se, Te), Ge-As-X, Ge- Sb- X, Qe- P- X Chalcogenide glasses have high transparency in the IR region of the spectrum, possess electronic conductivity, and exhibit an internal photoelectric effect. Glasses are used in television highly sensitive cameras, in electronic computers as switches or elements of storage devices.
oxide glasses are a broad class of compounds. The oxides SiO 2 , GeO 2 , VgO 3 , and P 2 O 5 form glasses most easily.
A large group of oxides - TeO 2, TiO 2, SeO 2, WO 2, Bio 5 ,
For example, glasses are easily formed in the systems CaO-Al 2 O 5, CaO-MgO 3 -BaO 3, P 5 O 5 - ws.
Each of the glass forming oxides can form glasses in combination with intermediate or modifying oxides. Glasses are named according to the type of glass-forming oxide: silicate, borate, phosphate, germanate, etc. Of practical importance are glasses of simple and complex compositions belonging to silicate, borate, borosilicate, phosphate, germanate, aluminate, molybdate, tungstate, and other systems.
Industrial glass compositions usually contain at least 5 components, while special and optical glasses can contain more than 10 components.
The most important advantage of glass technology is that it makes it possible to obtain substances in the solid state with a non-stoichiometric ratio of components that do not exist in the crystalline state. Moreover, the properties of glasses can be smoothly adjusted in the desired direction by gradually changing the composition.
Glasses obtained on the basis of nitrate, sulfate and carbonate compounds are currently of scientific interest, but have not yet been applied in practice.
The traditional technology for producing glasses includes supercooling the melt to a solid state without crystallization. The world industrial glass production technology is based on this method.
The creation of technical devices that allow heat to be removed at a higher rate expands the number of substances that can be obtained in a glassy state by cooling the melt. Ultrahigh supercooling rates of the order of several million degrees per 1 s make it possible to fix metal alloys in the glassy state (for example, in the Fe-Mi-B-P system).
Methods for obtaining glasses by vacuum evaporation, condensation from the vapor phase, and plasma spraying are gaining industrial importance. In these cases, glass can be obtained from the gas phase, bypassing the molten state.
Irradiation of crystals with high-energy particles or exposure to a shock wave leads to a random displacement of particles from their equilibrium positions and, thus, to amorphization of the structure, as a result of which solid crystalline substances can be transferred to a glassy state, bypassing the melting stage.
Inorganic glasses are classified by type of glass-forming substance, type of modifiers, manufacturing technology and appointment.
According to the type of glass-forming substance, inorganic glasses are divided into silicate(SiO2), aluminosilicate(A1 2 0 3 -SiO 2), borosilicate(B 2 0 3 -SiO 2), aluminoborosilicate(A1 2 0 3 -B 2 0 5 -SiO 2), aluminophosphate(А1 2 0 3 –Р 2 0 5), chalcogenide(for example, As 31 Ge 30 Se 21 Te 180), halide and other glasses.
According to the type of modifiers, they distinguish alkaline, non-alkaline and quartz inorganic glasses. The strength of alkaline glass under the action of moisture is halved, since water leaches the glass. In this case, alkaline solutions are formed, which wedged the glass, causing the appearance of microcracks in the surface layer.
According to the manufacturing technology, inorganic glass can be obtained blowing, casting, stamping, drawing into sheets, tubes, fibers, etc. Glass is produced by industry in the form of finished products, blanks, and individual parts.
By purpose, inorganic glasses are divided into technical, building and household(glass containers, dishes, household, etc.).
Technical glass by area of application is divided for electrical, transport; optical, lighting, heat-resistant, refractory, fusible, chemical laboratory and etc.
Electrical glass. High electrical resistivity, high electrical strength (16–50 kV/mm), low dielectric loss (tgδ=0.0018–0.0175) and relatively high dielectric constant (ε=3.5–16), which increases with an increase in the concentration of PbO or BaO. When heated in the temperature range of 200–400 °C, the electrical resistivity decreases by a factor of 108–1010, which is associated with an increase in the mobility of alkali ions, and the glass loses its insulating properties. Oxides of heavy metals - lead and barium reduce the mobility of ions and reduce losses.
When soldering metal into glass, when welding glasses of different composition, thermal stresses appear in the glass due to the difference in the temperature coefficients of linear expansion. If the temperature coefficients of both materials are close, then glass junctions with the material are called matched junctions, and if they are different mismatched junctions.
As a dielectric, it is used for bulbs of lighting lamps and radio tubes, in electric vacuum devices, for insulators, for sealing integrated circuits. Thus, in the form of a thin (up to 3–4 µm) film, glass is used as a strong, non-cracking, and heat-resistant insulation on metal wires and thermocouples. Chalcogenide glass is used to encapsulate semiconductor devices. Electrically conductive (semiconductor) glasses: chalcogenide and oxide vanadium - are widely used as thermistors, photoresistors.
Electrical glasses, depending on the value of the temperature coefficient of linear expansion, are divided into platinum (C89-2), molybdenum (C49-1) and tungsten (C38-1). Each glass group is used for matched junctions with Mo, W and Fe-N alloys. The brand of electrical glass indicates the value of the temperature coefficient of linear expansion.
Transport glass. In mechanical engineering, it is effectively used as a structural material, provided that brittleness is neutralized, which is achieved by hardening it, as a rule, in an air stream.
The specific properties of glasses are their optical properties: translucency, reflection, scattering, absorption and refraction of light. The refractive index of such glasses is 1.47–1.96, the scattering coefficient is in the range of 20–71.
The types of transport glass are triplexes and thermopan, used for glazing in vehicles, space suits.
Triplexes - composite material obtained from two sheets of tempered silicate (or organic) glass 2-3 mm thick, glued together with a transparent elastic polymer (usually from polyvinyl butyral) film. When the triplex is destroyed, the formed non-sharp fragments are retained on the polymer film.
Thermopan - three-layer glass, consisting of two sheets of tempered glass and an air gap between them. This air layer provides thermal insulation.
Optical and lighting glass. The optical properties of glasses depend on their color, which is determined by the chemical composition of the glasses, as well as on the state of the surface of the products. Optical products should have an isotropic, stress-free annealed structure and smooth, polished surfaces.
Ordinary unpainted sheet glass transmits up to 90%, reflects about 8%, and absorbs about 1% of visible and partially infrared light; ultraviolet radiation is absorbed almost completely. Quartz glass is transparent to ultraviolet radiation. Light-diffusing glasses contain fluorine in their composition. Glass with a high content of PbO absorbs X-rays.
Optical glasses used in optical devices and instruments are divided into crowns, characterized by low refraction (n d \u003d 1.50), and flints(n d \u003d 1.67) - with a high content of lead oxide.
Heat-resistant and refractory glass.
Pyrex - heat-resistant glass based on SiO 2 (80.5%) with a high content of B 2 0 3 (12%), Na 2 0 (4%), as well as oxides of aluminum, potassium and magnesium.
"Mazda" - refractory glass based on SiO 2 (57.6%) with oxides of aluminum (25%), calcium (7.4%), magnesium (8%) and potassium. "Pyrex" and "Mazda" are used for the manufacture of products used at elevated operating temperatures: thermometer shells, sight glasses, etc.
Lightweight glass. These glasses are made on the basis of PbO (70%) with the addition of B 2 O 3 (20%) or B 2 0 3 (68.8%) with the addition of ZnO (28.6%) and Na 2 O (2.6%) ; are used for the manufacture of enamels, glazes and solders for soldering glass.
building glass produce the following types: sheet, facing and glass products and structures.
Sheet glass is made from glass mass, which includes 71–73% SiO 2, 13.5–15% Na 2 O, up to 10% CaO, up to 4% MgO and up to 2% A1 2 0 3. The mass of 1 m 2 of sheet glass is 2–5 kg. Light transmission - not less than 87%.
Sheet glass is produced in three grades and, depending on the thickness, six sizes (grades): 2; 2.5; 3; 4; 5 and 6 mm. The grade of sheet glass is determined by the presence of defects, which include: banding - unevenness on the surface; svil - narrow threadlike stripes; bubbles - gas inclusions, etc. The width of the glass sheets is 250–1600 mm, the length is 250–2200 mm.
The industry also produces special types of sheet glass: showcase(polished), heat-absorbing, uviole(transmitting 25-75% of UV rays), hardened, architectural and construction and etc.
Sheet glass is the main type of glass used for glazing window and door openings, shop windows, exterior and interior decoration of buildings.
Facing glass is applied to finishing of facades and internal rooms of the building. The consumer properties of such glass include high decorativeness (bright colors, shiny surface), great weather resistance and durability. The group of facing glasses includes:
stemalite - sheet building material made of tempered polished (6–12 mm thick) glass, coated on the inside with opaque (deaf) ceramic paint. The coating is protected from the room side by a thin layer of aluminum deposited in a vacuum. It is applied to internal and external facing of buildings;
marblit - sheet building material 12 mm thick made of colored opaque glass with a polished front surface and a corrugated back, can imitate marble;
glass enamel tiles made from waste sheet glass (glass enamel) welded onto the surface of glass cut to the required dimensions (150x150, 150x70 mm with a thickness of 3–5 mm);
glass mosaic - carpet mosaic in the form of small square tiles (20x20 or 25x25 mm) made of opaque (muted) colored glass, laid out in plain or mosaic carpets;
smalt - cubes or plates 10 mm thick of colored opaque glass, obtained by casting or pressing; used for making mosaics.
Glass products and structures. The most common glass products and structures in the construction industry include:
glass blocks - hollow blocks of two molded halves welded together. Light transmission - not less than 65%, light scattering - about 25% (light scattering is increased by corrugation of the inner side of the blocks), thermal conductivity - 0.4 W / (m K). They are used to fill light openings in external walls and to install translucent coatings and partitions;
double-glazed windows - two or three sheets of glass connected along the perimeter by a metal frame (clip), between which a hermetically closed air cavity is created. Are applied to a glazing of buildings;
glass profile - large-sized building panels made of profile glass, produced by the method of continuous rolling of box-shaped, tee, channel and semicircular profiles. Glass profiles can be reinforced and non-reinforced, colorless and colored. It is applied to the device of translucent protections of buildings and constructions.
Fiberglass - fibrous material obtained from molten glass. The most widely used are alkali-free alumina-borosilicate E-glass, as well as high-strength glass based on oxides: SiO 2 , A1 2 0 3, MgO. The glass fiber diameter ranges from 0.1 to 300 microns. The shape of the section can be in the form of a circle, square, rectangle, triangle, hexagon. Hollow fibers are also produced. By length, the fiber is divided into staple (from 0.05 to 2–3 m) and continuous. Fiberglass density 2400–2600 kg/m 3 . The strength of elementary glass fibers is several tens of times higher than bulk glass samples: the tensile strength reaches 1500–3000 MPa for continuous fibers with a diameter of 6–10 μm. Fiberglass has high thermal, electrical and sound insulation properties, it is thermally and chemically resistant, non-flammable, and does not rot.
The surface of glass fibers during transportation and various types of processing is oiled to prevent abrasion, since their strength depends on the state of the surface of the fibers. Made from fiberglass glass wool, fabrics and grids, as well as nonwovens in the form of bundles and canvases, glass mats.
Glass wool - material made of glass fibers, the diameter of which for the manufacture of heat-insulating products should not exceed 21 microns. The structure of cotton wool should be loose - the number of strands consisting of parallel fibers should not exceed 20% by weight. The loose density should not exceed 130 kg/m 3 . Thermal conductivity - 0.05 W / (m K) at 25 ° С. Glass wool from a continuous fiber is used for the manufacture of heat-insulating materials and products at temperatures of insulated surfaces from -200 to +450°C.
Super fine fiber glass wool has a density of 25 kg / m 3, thermal conductivity of 0.03 W / (m K), operating temperatures from -60 to +450 ° C, sound absorption of 0.65–0.95 in the frequency range of 400–2000 Hz. Superfine glass wool, as well as products based on it, are used in construction as a soundproofing material.
Glass mats(ASIM, ATIMS, ATM-3) - materials consisting of glass fibers located between two layers of fiberglass or fiberglass mesh quilted with glass threads. They are used at temperatures of 60–600°C as reinforcing elements in composite materials.
Glass roofing material and fiberglass - roll materials obtained by double-sided application of a bituminous (bitumen-rubber or bitumen-polymer) binder, respectively, on a glass fiber canvas or glass felt and coating on one or both sides with a continuous layer of dressing. The combination of a biostable base and impregnation with enhanced physical and mechanical properties makes it possible to achieve durability for glass roofing material of about 30 years.
Depending on the type of dressing that prevents sticking when stored in rolls, and the purpose of the glass roofing material, the following grades are produced: S-RK (with coarse-grained dressing), S-RF (with scaly dressing) S-RM (with dust-like or fine-grained dressing). Glass roofing material is used for the upper and lower layers of the roofing carpet and for glued waterproofing.
Gidrostekloizol - waterproofing roll material intended for waterproofing reinforced concrete lining of tunnels (grade T), superstructures of bridges, overpasses and other engineering structures (grade M).
Gidrostekloizol consists of a glass base ( woven or non-woven retina, doubled with fiberglass), coated on both sides with a layer of bituminous mass, which includes bitumen, mineral filler (about 20%) with ground talc, magnesite, and a plasticizer. It differs in addition to high water resistance by good tensile strength in the longitudinal direction. It withstands breaking load at the highest quality category of 735 N. Heat resistance - 60–65 °С, brittleness temperature - from -20 to -10 °С.
Hydrostekloizol is glued without the use of mastics - by uniform melting (for example, using a gas burner flame) of its surface.
Foam glass (cellular glass)- a cellular material obtained by sintering finely divided glass powder and a blowing agent. They are produced from cullet or use the same raw materials as for the production of other types of glass: quartz sand, limestone, soda and sodium sulfate. Pore formers can be coke and limestone, anthracite and chalk, as well as calcium and silicon carbides, which release carbon dioxide during sintering, which forms pores.
Foam glass has a specific structure - the material of the walls of large pores (0.25–0.5 mm) contains the smallest micropores, which leads to low thermal conductivity (0.058–0.12 W / (m K)) with sufficiently high strength, water resistance and frost resistance . The porosity of various types of foam glass is 80–95%; density 150–250 kg / m 3; strength 2–6 MPa. It has high heat and sound insulation properties. Foam glass is a fireproof material with high (up to 600 °C) heat resistance. Easily processed (sawed, polished); it adheres well to, for example, cementitious materials.
Foam glass shields are used for thermal insulation of building envelopes (walls, ceilings, roofs, etc.), in refrigerator structures (insulation of surfaces with an operating temperature of up to 180 ° C), for decorative interior decoration. Filters for acids and alkalis are made from open-pore foam glass.
Glasspore obtained by fanulation and swelling of liquid glass with mineral additives (chalk, ground sand, TPP ash, etc.). Three grades are produced: SL ρ 0 \u003d 15–40 kg / m 3, λ \u003d 0.028–0.035 W / (m K); L ρ 0 \u003d 40–80 kg / m 3, λ \u003d 0.032–0.04 W / (m K); ρ 0 \u003d 80–120 kg / m 3, λ \u003d 0.038–0.05 W / (m K).
In combination with various binders, glass pores are used for the manufacture of piece, mastic and poured thermal insulation. The most effective use of glass pores is in unfilled foam plastics, since its introduction into the foam plastic makes it possible to reduce polymer consumption and significantly increase the fire resistance of heat-insulating products.
Reinforced glass - a structural product obtained by the method of continuous rolling of inorganic glass with simultaneous rolling inside a sheet of metal mesh from annealed chrome-plated or nickel-plated steel wire. This glass has a compressive strength of 600 MPa, increased fire resistance, shatterproof in case of destruction, light transmission - more than 60%. It may have a smooth, forged or patterned surface, be colorless or colored.
Reinforced glass is used for glazing skylights, window casings, partition walls, flights of stairs, etc.
Sitally
Glass-ceramics (glass-ceramic materials) - artificial material based on inorganic glass, obtained by complete or partially controlled crystallization in them.
The term "sitalls" is derived from the words: "glass" and "crystals". According to the structure and production technology glass-ceramics occupy an intermediate position between ordinary glass and ceramics. They differ from inorganic glass in their crystalline structure, and from ceramic materials in a finer-grained and homogeneous microcrystalline structure.
The composition of sitalls includes:
oxides - Li 2 0, A1 2 O 3, SiO 2, Mg0, CaO, etc.;
nucleators(crystallization catalysts) - salts of light-sensitive metals -Au, Ag, Cu, which are colloidal dyes and are present in glass in the form of fine particles. Nucleators are additional crystallization centers (Fig. 13). They must have a crystal lattice similar to crystalline phases emerging from glass, and contribute to uniform crystallization of the entire mass;
mufflers(poorly soluble particles) - fluorine and phosphate compounds, TiO 2, etc.
The structure of glass-ceramics is fine-crystalline, homogeneous, characterized by the absence of porosity. The average size of crystallites in glass-ceramics is 1–2 μm. The content of the crystalline phase is at least 40–50%. Crystallites grow together or are connected by interlayers of residual amorphous glass. The amount of glass phase does not exceed a few percent. Random orientation of crystallites leads to the absence of anisotropy in glass-ceramics.
By adjusting the heat treatment modes, it is possible to change the degree of crystallization and the size of the crystals, which affects the properties of the product. The properties of glass-ceramics are isotropic and are mainly determined by the phase composition and their structure. The main properties of glass-ceramics are:
Density 2400–2950 kg / m 3;
Softening temperature 1250–1350 °С;
Low thermal conductivity 2–7 W/(m K);
Temperature coefficient of linear expansion (7–300)·10 -7 °C -1 .
σco=7–2000 MPa, σin=112–160 MPa, σbend=7–350 MPa;
Young's modulus 84–141 GPa;
Brittleness (with impact strength 4.5–10.5 kJ / m 2);
Microhardness - 7000–10500 MPa;
High wear resistance;
Heat resistance - 200–700°С (up to 1100°С);
Dielectric properties;
Chemical resistance;
Gas-tight and zero water absorption.
Rice. 13. Scheme of crystallization of glass during the formation of glass-ceramics
using nucleators.
In appearance, sitalls can be opaque (deaf), transparent, and also colored (dark, brown, gray, cream and light colors). Their strength depends on temperature: up to 700–780 °C, it decreases insignificantly, and at higher temperatures it drops rapidly. The heat resistance of glass-ceramics is 800–1200 °C.
The reason for the particularly valuable properties of glass-ceramics lies in their exceptional fineness and almost ideal polycrystalline structure. There is absolutely no porosity in them. The shrinkage of the material during its processing is negligible. Great abrasive resistance makes them insensitive to surface defects.
Glass-ceramic parts are connected to each other and other materials using glass-ceramic cement, followed by heat treatment at 400–600 ° C, adhesives and putties based on epoxy resin and liquid glass, metallization, followed by soldering.
Sitalls are classified according to on the method of production, on the nature of the raw materials and on the intended purpose.
Glass-ceramic products are obtained, as a rule, by melting a glass charge of a special composition, cooling the melt to a plastic state and subsequent molding by glass or ceramic technology methods (drawing, blowing, rolling, pressing), and then glass-ceramicization. Such products are also obtained by powder sintering.
By the nature of the starting materials and properties, there are: petrositalls, slag-sitaly and technical sitalls. A variety of sitalls are glass-ceramics - composite materials obtained on the basis of plastics (fluoroplasts) and glass-ceramics.
Petrositalls are obtained on the basis of gabbro-norite, diabase and other rocks, slag-ceramics are obtained from metallurgical or fuel slags. Technical glass-ceramics are made on the basis of artificial compositions from various chemical compounds - oxides, salts.
According to their purpose, sitalls are divided into structural(construction and engineering), technical, radio, electrical and phototechnical. On the basis of sitalls, various adhesives are obtained for bonding metal, glass, and ceramics. The most widely used in construction slag-ceramics and foam-slag-ceramics.
Slag-ceramics - glass-ceramics from fiery-liquid metallurgical slags. Density - 600–2700 kg / m 3; σcomp=250–550 MPa, σbend=65–130 MPa, modulus of elasticity E= 11 10 4 MPa, operating temperatures - up to 750 ° C, water absorption is practically zero; high acid and alkali resistance.
Slag-ceramic products are cheap and highly durable. These products are used for stairs, floor tiles, internal partitions, as roofing and wall material, for facing critical parts of hydraulic structures, as well as in road construction as slabs for sidewalks, road surfaces. Slag-ceramic sheet (any color can be obtained) is used as a decorative and finishing material for exterior and interior cladding of structures. Slag-ceramics can be obtained in any color, and in terms of durability they compete with basalts and granites.
Foam-slag-ceramic - foamed slag-ceramic with a cellular structure. Effective thermal insulation material with low water absorption and low hygroscopicity. Operating temperatures - up to 750 ° C Foam-slag-ceramics are used for wall insulation and soundproofing of rooms, as well as for insulating heating pipelines and industrial furnaces.
In mechanical engineering glass-ceramics are used for the manufacture of bearings, engine parts, pipes, heat-resistant coatings, compressor blades, precise gauges for metal-cutting machines, metrological measures of length, dies for drawing synthetic fibers, abrasives for grinding; in chemical engineering - friction pairs of plungers, parts of chemical pumps, reactors, stirrers, shut-off valves. Radio and electrical glass-ceramics are used for the manufacture of substrates, shells, plateaus, mesh screens, radome antennas, etc., as well as heat-resistant coatings for protecting metals from high temperatures. Phototechnical glass-ceramics are used for the manufacture of mesh screens for televisions, road signs, telescope mirrors, for replacing photo-emulsions of transparencies, on instrument scales, etc. The resolution and image quality of photo-glasses are higher than those of ordinary photo-emulsions.
4.4. Questions on the topic "Glasses":
1. What is the structure of glass? What is in glass?
2. How is glass classified according to its chemical composition and purpose?
All solids in nature are either crystalline or amorphous (glassy) state.
Crystalline bodies have a regular geometric lattice, which is formed by particles (ions or atoms) arranged in a strictly repeating order. Unlike crystalline bodies, vitreous substances do not have such a lattice. The particles that make up the glass are arranged geometrically correctly, only in relative proximity to each other, and at some distance this order is violated. In other words, we can say that there is no correct order in the arrangement of elementary geometric cells in glass. Therefore, sometimes crystalline bodies are characterized as materials having a long-range order, and glass as a material having only a short-range order.
Glass refers to all amorphous bodies obtained by supercooling the melt, regardless of the chemical composition and temperature range of solidification, and possessing the properties of solids as a result of a gradual increase in viscosity; the process of transition from a liquid to a glassy state must necessarily be reversible.
There are also a number of other distinctive features inherent in glasses. For example, crystalline bodies are characterized by a constant melting point for each substance. Glasses soften in a wide range of temperatures. The properties of crystalline bodies during their solidification in the process of crystallization change abruptly, that is, suddenly, while the properties of glasses change gradually during their solidification.
Glasses are divided into natural and artificial.
Natural glass includes glass formed during the activity of volcanoes (magma eruptions), such as obsidian glass.
Artificial glasses include all glasses created as a result of human labor.
Artificial glasses, in turn, are organic and inorganic.
Organic glasses (plastics) are produced on the basis of products of organic origin, mainly resins. Due to insufficiently high transparency, low durability, and low chemical resistance, organic glass has not found wide distribution.
Inorganic glass is obtained from inorganic materials. Depending on the glass-forming oxide on the basis of which glass is made, the following types of glass are distinguished:
silicate, obtained on the basis of silicon dioxide SiO 2;
borate - based on boron oxide B 2 O 3;
borosilicate - based on B 2 O 3 and SiO 2;
phosphate - based on phosphoric anhydride P 2 O 5.
Along with those listed, the glass contains oxides of sodium (Na 2 O), potassium (K 2 O), calcium (CaO), magnesium (MgO), aluminum (Al 2 O 3), barium (BaO), lead (PbO), zinc (ZnO), manganese (MnO), copper (CuO).
Depending on the purpose, industrial glass is divided into building, technical, electrovacuum, optical, chemical-laboratory, container, and high-quality glass.
The building glass group includes sheet window (GOST 111-65) and display glass, unpolished, polished (GOST 7132-61) and sheet reinforced (GOST 7481-67), patterned (GOST 6629-74), structural and building elements (hollow glass blocks, profiled glass), architectural and artistic glass (colored sheet glass, glass mosaic and facing tiles). All these glasses are silicate. Approximate compositions of industrial glasses are shown in Table 1.
| Glass | SiO2 | Al 2 O 3 | Cao | MgO | Na2O | K2O | B2O3 | BaO | F | PbO |
|---|---|---|---|---|---|---|---|---|---|---|
| Window Polished tare Varietal Chemical laboratory Electrovacuum Optical crystal |
71,6 73,2 73,7 74,5 68,7 71,9 53,5 57,5 |
1,5 1,3 0,2 0,5 3,8 - 8,8 0,5 |
7,8 7,8 9,1 6,5 8,4 5,5 - - |
4,0 3,8 1,75 2,0 0,8 3,5 - - |
15,1 13,9 15,2 14,0 9,7 16l - - |
- - - 2,0 6,1 1,0 16,2 15,5 |
- - - - 2,5 - 16,2 1,0 |
- - - - - 2,0 ZnO 1,0 |
- - - - - - 5,3 - |
- - - - - - - 24 |
Electrovacuum glasses. The determining parameter of glasses for the manufacture of cylinders, legs and other parts of electrovacuum devices is the temperature coefficient of linear expansion. It is very important when soldering and welding various glasses, when soldering metal wire or tape into glass. Values α l the glass and the materials connected to it should be approximately the same, since otherwise, when the temperature changes, the glass may crack, as well as leakage at the point where the metal wire is inserted into the glass. In addition, glasses with low dielectric losses are used for high-frequency devices. Electrovacuum glasses are subdivided and labeled according to the numerical values of the temperature coefficient of linear expansion. Since glasses are materials with a small value of the temperature coefficient of linear expansion, and for metals there is a natural relationship between the melting temperature and the value of the temperature coefficient of linear expansion, it is possible to solder into glasses only refractory metals or metal alloys, in which α l the same as for refractory metals.
Therefore, electrovacuum glasses are divided into:
According to the chemical composition, electrovacuum glasses belong to the group of borosilicate (B2O3 + SiO2) or aluminosilicate (Al2O3 + SiO2) materials with additions of alkali oxides. The names "platinum", "molybdenum", "tungsten" are determined not by the composition of the glass, but only by the fact that the values of α l of these glasses are close to α l, platinum, molybdenum, tungsten. The temperature coefficient of linear expansion increases with an increase in the content of alkali oxides. In the designation of the brand of electrovacuum glass after the letter C indicate the value α l and development series. For example, grade C89-5 characterizes glass with α l= 89 10–7 K–1 of series 5.
insulating glasses. Glasses are easily metallized and used as hermetic bushings in metal cases of various devices (capacitors, diodes, transistors, etc.). Another insulating element often found in discrete semiconductor devices is a glass bead, which isolates the metal leads of the device from the housing flange, on which the semiconductor crystal is located. p-n-transitions. Glass beads are made from capillaries cut into tubes and rings of certain sizes. Usually, alkaline silicate glass is used as the material of such bushings.
colored glass. Ordinary silicate glasses are transparent to radiation in the visible part of the spectrum. Some additives give glasses the appropriate color: CaO - blue, Cr2O3 - green, MnO2 - violet and brown, UO3 - yellow, etc., which is used in the manufacture of colored glasses, filters, enamels and glazes.
Laser glasses. Glass can be used as a working medium in solid-state lasers. The generating centers are active ions uniformly distributed in a dielectric transparent matrix. As a rule, there are no restrictions on the solubility of activating additives in glasses. In practice, barite crowns (BaO - K2O - SiO2) activated with neodymium ions Nd3 + are most often used.
The main advantages of glasses used in lasers over single crystals are their high manufacturability, optical homogeneity, and isotropy of properties. It is comparatively easy to fabricate uniform rods of large size from glass, which is necessary to achieve a high output power of laser radiation. However, the absence of long-range order causes broadening of the luminescence lines of the activated glass. The consequence of this is a decrease in the degree of monochromaticity of the output radiation and an increase in the threshold power of the optical pump. In addition, glasses, in comparison with single crystals, have a low thermal conductivity, which creates additional difficulties for the implementation of a continuous generation mode. Therefore, glass lasers are better suited for generating high-energy pulses.
Fiberglass. From molten glass mass by drawing through a spinneret followed by rapid winding on a rotating drum, it is possible to obtain thin fibers with good flexibility and increased mechanical strength. The great flexibility and strength of fiberglass is due to the orientation of the particles of the surface layer of glass, which occurs when the fiberglass is drawn from the molten glass mass and rapidly cooled. Very thin glass fibers (4–7 µm in diameter) have such high flexibility that they can be processed by textile technology. Glass threads spun from individual fibers are woven into glass fabrics, ribbons and hoses. The advantages of glass fiber insulation over organic fiber insulation are high heat resistance, significant mechanical strength, relatively low hygroscopicity, and good electrical insulating properties. Alkaline aluminosilicate, alkali-free and slightly alkaline aluminoborosilicate glasses are used for the production of fiberglass.
Light guides. Thin glass fibers are used to transmit light between a source and a receiver. Individual fibers can be connected into light cables (bundles) with internal interfiber light-insulating coatings. The combination of methods and means of transmitting light information using the thinnest fibers is called fiber optics, which is an important part of optoelectronics.
Fiber devices have a number of advantages over lens devices. They are compact and reliable. With their help, it is possible to carry out element-by-element image transmission with a sufficiently high resolution, and image transmission is possible along a curved path. An essential point is the secrecy of information transmission and the high noise immunity of the optical communication channel, in which the fibers themselves play the role of light guides, i.e. serve as guiding systems - they channel the light from the source to the receiver of information. The guiding action of the fibers is achieved due to the effect of multiple total internal reflection (Fig. 6).
Rice. 6. Explanation of the principle of operation of the light guide
For image transmission, fibers with a diameter of 5–15 µm are used. To prevent light from leaking from one fiber to another, they are provided with a light-insulating sheath, which is made of glass with a lower refractive index than that of the core. Then the light beam L falling from a medium that is optically denser ( P 1 - larger), to the interface with the medium, optically less dense ( n 2 - smaller), at an angle greater than the limit, will experience total internal reflection and, being reflected many times, will go along the fiber, as shown in the segment of a separate fiber (Fig. 6). An image of an entire object, such as a letter To on the page of a book, can be transmitted along a bundle of bent fibers if the transmitting end of the light guide 1 put on the object illuminated by the light guide; at the receiving end of the fiber 2 the image will be tiled, as shown at the top of fig. 6. A light cable with a diameter of 5–6 mm contains several hundred thousand light-insulated fibers. For correct image transmission, regular laying of the fibers in the bundle is required, i.e. the relative arrangement of the fibers at its input and output ends should be the same.
With the help of fiber bundles, it is easy to carry out the transformation of an optical image, its encoding and decoding. Light cables made of fibers with a conical section can enhance the illumination of objects due to the concentration of the light flux, reduce or enlarge the image.
Special technological methods (film deposition on a substrate, ion doping, ion exchange) make it possible to manufacture flat light guides, which are the basis of optical integrated circuits.
Glass products are classified;
According to the method of molding (working out);
Dimensions;
Types and complexity of decoration;
completeness;
Appointment.
By molding method glass products are divided into:
For pressed;
Press-blown;
blown;
drawn;
Bent.
Pressed glass products are produced in a mold at one time from a portion of glass mass manually or mechanically under the pressure of a punch inserted into the mold.
Press-blown products are produced from a portion of glass mass placed in a draft mold and subsequently inflated in a clean mold with air from a compressor.
Blown products, in turn, are divided into hand-blown glass products and mechanized blown glass products.
Hand-blown glass products are produced by hand using a molded blow tube or by free blowing.
Mechanized blown glass products are produced from a portion of glass mass fed into a clean mold and then blown while rotating.
Drawn products are obtained by casting, joining, rolling, centrifuging and drawing.
Curved glass products are produced by heating a glass blank to a softening temperature and bending it under the action of its own weight and / or using a pressing device to the final shape.
A multi-stage glass article is produced by joining individual glass elements made in two or more stages.
An overlay glass product is produced by fusing two or more layers of glass of different colors. The coefficients of thermal expansion of these glass masses must be the same.
A combined glass product is produced by combining glass with other materials.
A product made of centrifuged glass is made in one go from a portion of glass mass under the action of centrifugal force.
The strengthened product is produced from glass of increased mechanical strength, achieved through thermal and / or chemical treatment and / or a special method of production from several layers of glasses of different composition.
Classification in form. The shape of the product must be combined with its functional purpose, aesthetic and hygienic features, as well as be consistent with the possibilities of the molding method and the properties of glass. The shape should create ease of use of the product, as well as be stable and ensure a long service life.
Glass products are divided into hollow and flat.
Hollow - decanters, jugs, glasses, wine glasses, glasses and vases. Their shapes are very diverse (cylindrical, conical, oval, spherical, etc.).
Flat - plates, dishes, cabarets of various configurations (oval, rectangular, round, multifaceted).
Hollow dishes - products having an internal depth of not more than 25 mm, measured from the lower internal point to a horizontal plane passing through the edge (overflow point).
By size glass household products are divided into small, medium, large, extra large.
Small - height up to 100 mm (Guten products - up to 160 mm), diameter up to 100 mm (Guten products - up to 160 mm), capacity up to 100 ml; Guten products are produced by blow molding without a mold.
Medium - height from 100 to 250 mm (Guten products - from 160 to 23 mm), diameter from 100 to 150 mm (Guten products - from 160 to 230 mm "capacity from 100 to 500 ml.
Large - height over 250 mm (Guten - 230 mm), diameter over 150 (Guten - over 230 mm), capacity over 500 ml.
Especially large - height over 350 mm, diameter over 250 mm, capacity over 1500 cm 3.
Product classification by type and complexity of decoration. The artistic and decorative value of glass products is increased by various decoration methods (the cuts applied to glass products are diverse in nature, application method, complexity, color and other features).
There are cuts applied to products in a hot state (during production) and in a cold state (finished products).
The type of decoration depends on the purpose of the product, its shape, production method, chemical composition and other features.
Hot Decorated Items
Free-blown glass products (bent glass products) are molded and decorated in a viscous-plastic state using tools designed for this operation.
Pointed glass products are made from colorless glass with additives, which, upon subsequent cooling and reheating, acquire color.
Products made of crackle glass are decorated by rapid cooling of the set in water or wet sawdust to form thin surface cracks, which recover with further heating and working out. Products with crackle cutting have low strength and thermal stability.
Glass products with optical effect m it is first blown in a mold that is smaller than the finished product and has a pattern in the form of edges, waves, etc. Then it is placed in a slightly larger mold with a smooth inner surface. Finally, the products are blown out, rotating in the mold, while the edges and waves on the surface are smoothed and remain only in the thickness of the walls.
Embossed glass products are produced in relief shapes by pressing or blowing.
Glass products with gas inclusions are decorated with air ribbons, threads and bubbles.
Glass products with foreign inclusions are obtained by fusing various objects made from other materials into the glass mass.
Glassware with an ornament is decorated with moldings, chips, rods, ribbons, threads, followed by heating or a set of glass and its further shaping (decoration with filigree or twisting, embankment, fiberglass).
Cold-decorated glassware.
The assortment of these products is more diverse in comparison with products decorated while hot.
Cuts are applied to finished products by mechanical and chemical methods, as well as by surface decoration.
Glass products decorated in a cold state by mechanical means include:
Flat edge glass products , decorated with grinding or polishing surfaces using an abrasive wheel or abrasive material.
Glass products with a diamond edge , decorated by applying facets in different directions along the profile and depth using abrasive material.
To speed up work in the molding process, the contours of the pattern are applied to the glass products, which are then polished with special circles.
Products with matte polishing are decorated on a grinding wheel without subsequent polishing.
Engraved products are decorated with ultrasound, laser or engraving tools.
cutting, applied chemically or by etching, may be transparent or opaque. This method of decorating glass products consists in destroying the surface of the glass with hydrofluoric acid or fluorine salts. Products are pre-coated with a protective layer of black wax and paraffin. After that, the products are placed in pickling baths from a mixture of hydrofluoric hydrochloric and sulfuric acids (acid destroys the glass surface without a protective layer), and a matte pattern is formed. If the bath contains a mixture of hydrofluoric and sulfuric acids, then the pattern is transparent.
Etching according to the complexity and depth of the pattern is distinguished:
Simple;
Complex;
Deep artistic.
Simple etching is a simple repeating pattern in the form of broken spirals and zigzag lines. The drawing is applied on galotire machines.
Complex etching - it is characterized by a more complex composition, the pattern of which is applied on special machines.
Deep artistic etching - decoration of two- and multi-layer products. The outer layer should be colored, and the inner one should be colorless.
Glass products with surface decoration - glass products decorated with silk-screen printing, spraying, decals.
By completeness glass household utensils are divided into piece and complete.
Piece products are produced in mass copies, different in composition of glass mass, purpose, shape, size, decorations.
Complete products , included in the kit must have a single style and compositional direction.
Set - a set consisting of several products of the same purpose and of the same type (in the amount of not more than six items).
Service - a set (set) consisting of two or more items of different types (for example, a bowl vase with a tray and six mugs).
By appointment glass products are divided into the following groups:
Glassware;
Decorative items;
Other products.
To the group glassware include glassware used in everyday life and catering, for preparing, serving and eating food, drinks and for table setting.
The range of dishes for serving food and drinks includes:
Dishes, cream vases;
Dishes for garnish;
Fruit vases; . "
Dishes for pies;
Carafes for water and beer;
Oil cans;
Herring;
sugar bowls;
Dishes;
salad bowls;
Vases for jam, sweets, cookies;
Teapots.
Dishes, plates, cake dishes - the most diverse in shape: oval, round with a cut-out edge and a smooth or with cutting along the edge "polishing with beads" of various sizes.
Dishes for garnish (cabarets) are oval, round, rectangular, irregular in shape with and without handles, with sections - three-seat, seven-seat.
Salad bowls in shape - round, square, figured; in the form of a bot, a rook; the edge of salad bowls is smooth, wavy, carved, with cutting along the edge "polishing with beads" of various sizes; salad bowls are made without legs or on one to four legs.
Butter dish - a product with a lid, on the lid - a holder.
herring - the product is oblong, oval, without legs.
Cream vase (kremanka) - a hollow product of a round, oval or cylindrical shape with a handle and a drain.
A decanter for wine or water is a hollow product of drop-shaped, figured shapes, in the form of a damask (rectangular) with a cork.
Fruit vase - a product with or without legs, of various shapes: spherical, round, in the form of baskets with and without handles, in the form of a boat, with a cut edge.
Creamers - products with handles and with a drain, they are oval, cylindrical in shape, on a pallet and without it.
Vases for jam, sweets, cookies are produced in the form of baskets with handles, in the shape of a boat, round, spherical, conical, figured on legs and beat them, with a carved or smooth edge or with cutting "polishing with beads". -
Sugar bowls - products in the form of square, round, spherical, cylindrical, oval without legs or on figured one or three legs.
In assortment utensils for eating and drinking include:
glasses, glasses, wine glasses, glasses for wine and beer, for champagne, for mineral and fruit waters, single-portion salad bowls. In the range of tea utensils - saucers, cups, saucers for jam, glasses for tea, cups for tea or coffee.
Products for taking drinks are issued on legs (glasses, glasses, wine glasses) and without legs (glasses).
Product shape the most diverse: shaped, conical, oval, teardrop-shaped, spherical, in the form of: hemisphere, tulip, bowl, cylindrical with an unfolded edge, tapering downwards, with an interception in the middle.
The legs of the products, in turn, are also diverse:
High and low;
Curly, smooth;
Sanded and unsanded.
According to the capacity of the product are divided:
For glasses with a capacity of 25 g;
Glasses with a capacity of 110-200 g;
Wine glasses with a capacity of 200-250 g;
Glasses with a capacity of 30-150 g.
To products without legs for drinking include glasses and mugs for beer.
Glasses depending on the capacity are divided:
For wine 25-100 g;
Beer 200-300 g;
Mineral and fruit waters 250-300 g;
Champagne 100-150 g.
Glasses in shape are: cylindrical, conical, oval, with a developed edge, with a jellied thickened bottom.
Mugs are a hollow product with a cylindrical, spherical handle.
Tableware range includes:
trays;
Trays of various shapes;
Ashtrays with different number of recesses for cigarettes;
Stands for napkins;
Napkin rings.
glass decorative items:
Applied art objects (flower vases);
Sculpture;
Souvenirs.
They are made both single copies and mass.
Artistic and decorative products differ in complex shape, size and various decorations (the most valuable and expensive cuts are applied to them).
A special place among artistic and decorative products is occupied by crystal products due to the specific properties inherent in crystal.
When tapped, crystal products emit a long melodic ringing. The sound effect is enhanced by an increase in the lead oxide content and a decrease in wall thickness: products with a drop-down shape have a greater sound effect.
A feature of crystal products is also a light effect, depending on the amount of lead and the angle of cutting. At a faceting angle of 90 degrees, the reflection of the light incident on the facet is greatest. The reflection coefficient is directly proportional to the content of lead oxides in the glass.
Crystal products are made massive and thick-walled, so they can be applied with deep diamond edges and thereby increase the reflection of light.
To other products relate:
Dressing table sets;
Stands for rings (jewelry);
Cigarette holders;