Types of ceramics. Depending on the structure, fine ceramics are distinguished from coarse ones. - The main types of fine ceramics are porcelain, semi-porcelain, earthenware, majolica. - The main type of rough ceramics is pottery ceramics. Porcelain has a dense sintered shard of white color (sometimes with a bluish tint) with low water absorption (up to 0.2%), when tapped it produces a high melodic sound, and can be translucent in thin layers. The glaze does not cover the edge of the bead or the base of the porcelain piece. The raw materials for porcelain are kaolin, sand, feldspar and other additives. Faience has a porous white shard with a yellowish tint, the porosity of the shard is 9 - 12%. Due to the high porosity, earthenware products are completely covered with a colorless glaze of low heat resistance. Earthenware is used to produce tableware for everyday use. The raw materials for the production of earthenware are white-burning clays with the addition of chalk and quartz sand. Semi-porcelain in properties occupies an intermediate position between porcelain and earthenware, the crock is white, water absorption is 3 - 5%, it is used in the production of tableware. Majolica has a porous shard, water absorption is about 15%, the products have a smooth surface, shine, thin walls, are covered with colored glazes and can have decorative relief decorations. Casting is used to make majolica. Raw materials - white-burning clay (faience majolica) or red-burning clay (pottery majolica), flux, chalk, quartz sand. Pottery ceramics have a red-brown shard (red-burning clays are used), high porosity, and water absorption up to 18%. Products can be covered with colorless glazes or painted with colored clay paints - engobes.

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“Eras of Culture” - Northern Renaissance. Post-Impressionism. Epochs of world culture. Modernism. Renaissance. Surrealism. Dadaism. Vanguard. Neoclassicism. Romanticism. Mannerism. High Renaissance. Baroque. Rococo. Cultural eras. Early Renaissance. Impressionism. Epochs. Cubism.

“Landscape art” - Vasilyevka (estate of N.V. Gogol). Play the role of an architect and create a fabulous sculpture. Dmitry Sergeevich Likhachev. Humpbacked bridge. Mother Earth. Grottoes (artificial caves). Staircase connecting the greenhouses. Mikhailovskoye (estate of A.S. Pushkin) Yasnaya Polyana (estate of L.N. Tolstoy). Fragrant plants.

“The state of water” - Aivazovsky’s Ninth Wave. Spring flood. A.S. Yesenin. I. Bunin. Thaw. Quietly slide along the glass and wander, Just as if you were looking for something fun... The hollow water is raging, The noise is both dull and drawn-out. Who is driving you away: is it destiny’s decision? N.K. Roerich. Test. Early snow. Solid state of aggregation of water. A.S. Pushkin.

“Architecture and painting of Germany and the Netherlands” - Albrecht Durer. Painting by German masters. Germany. Architecture and painting of Germany and the Netherlands. Frans Hals. Scandinavia. Architecture. Painting by German masters. Architecture of Germany. Painting by Dutch masters. Painting of the altar of the Church of St. Bavo. Four horsemen. Dutch painting.

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Historically, ceramics were understood as products and materials obtained from clays and their mixtures with mineral additives. Later, in order to impart hardness, water and fire resistance to clay products, firing began to be widely used. The word "ceramics" came to us from the ancient Greek language (keramos - baked clay, ceramics - pottery art).

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As technical progress progresses, a class of technical ceramics is formed. The concept of “ceramics” is beginning to acquire a broader meaning: in addition to traditional materials made from clays, it now includes materials obtained from pure oxides, carbides, nitrides, etc. The most important components of modern technical ceramics are aluminum oxides, zirconium oxides, silicon, boron, aluminum nitrides, silicon and boron carbides, etc.

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Advantages and prospects of ceramics exceptional variety of properties compared to other types of materials availability of raw materials low energy intensity of technology environmental friendliness of production biological compatibility The main producers of ceramics are the USA and Japan (38 and 48%, respectively). The USA dominates the field of structural ceramics. In Japan, along with the production of structural ceramics, the field of functional ceramics is developing dynamically.

Slide 5

Definition of "ceramics"

Ceramics are polycrystalline materials and products made from them, consisting of compounds of non-metals of groups III–VI of the periodic system with metals or with each other and obtained by molding and firing the corresponding raw materials. The starting raw materials can be either substances of natural origin (silicates, clays, quartz, etc.) or those obtained artificially (pure oxides, carbides, nitrides, etc.).

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Classification of ceramics by chemical composition

1. Oxide ceramics. These materials consist of pure oxides Al2O3, SiO2, ZrO2, MgO, CaO, BeO, ThO2, TiO2, UO2, oxides of rare earth metals, their mechanical mixtures (ZrO2-Al2O3, etc.), solid solutions (ZrO2-Y2O3, ZrO2-MgO etc.), chemical compounds (mullite 3Al2O32SiO2, etc.) 2. Oxide-free ceramics. This class consists of materials based on carbides, nitrides, borides, silicides, phosphides, arsenides and chalcogenides (except oxides) of transition metals and non-metals of groups III–VI of the periodic system.

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Classification of ceramics by purpose

1. Construction ceramics. 2. Thin ceramics. 3. Chemically resistant ceramics. 4. Refractories. 5. Technical ceramics.

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Classification of technical ceramics

1. Structural ceramics 2. Instrumental ceramics 3. Electro-radio ceramics 4. Ceramics with special properties

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Other classifications of technical ceramics

Traditional New Viscous Nanoceramics

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Ceramics structure

Crystalline phase - chemical compounds, solid solutions, interstitial phases. The amorphous phase is glass-forming oxide SiO2. Closed pores are those that do not communicate with the environment. Open pores – communicating with the environment.

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Indicators of porosity and density of ceramics

1. True (theoretical) density i, g/cm3 – density of non-porous material. 2. Apparent density к, g/cm3 – density of the material containing pores. 3. Relative density  = (k/i)100% . 4. True porosity Pi = (Vk-Vi)/Vk)100% = (1- k/i) 100%, – the total volume of all pores. 5. Apparent (open) porosity Pk = (Vot/Vk) 100% – the volume of open pores filled with water during boiling.

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Mechanical characteristics of ceramics

Typical   diagram for ceramics when tested up to ~ 1000С

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com, bend, HV, H, HRA, К1с, E, G Weibull formula Ryshkevich formula – dependence of strength on porosity, n=4...7 Young’s modulus Hooke’s modulus Poisson’s ratio

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Lecture 2

Thermomechanical, thermophysical and thermal properties of ceramics

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Thermomechanical characteristics of ceramics

Short-term strength at service temperature Deformation temperature under load Creep

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Scheme for determining the deformation temperature of ceramics under load. Limiting operating temperature tнр

Slide 17

Conditional creep limit is a stress that causes, during a specified test time at a given temperature, a specified elongation of the sample (total or residual) or a specified creep rate in the straight section of the creep curve.

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Primary creep curve: н – elongation under loading; п – full (elastic + residual) elongation on a curved section); с – total (elastic + residual) elongation during the test; у – elastic elongation; о – residual elongation.

Slide 19

Determination of the conditional creep limit of ceramics; a series of samples are tested at tset and 1-3; the average value of c, o, and d/d is determined in section II for each , diagrams  -  or  - d/d are drawn between in the section II in a logarithmic coordinate system, using these diagrams, find the creep limit 0.2, no less than at three t, construct a diagram 0.2 - t

Slide 20

Thermophysical properties

Heat capacity Thermal conductivity Thermal diffusivity Thermal expansion They are very important because determine the heat resistance of ceramics.

Slide 21

Heat capacity of ceramics

Cv=dE/dT Above D corresponds to the Dulong-Petit rule Cv=n3R: - for diatomic crystals Cv = 6R50 J/molK (MgO) - for triatomic – 9R75 J/molK (ZrO2) - for pentaatomic – 15R 125 J/molK (Al2O3)

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Thermal conductivity of ceramics

dQ/dt = -  dT/dx In oxide ceramics it has a phonon nature: ф = (1/3) Cvvф lф In oxide-free ceramics such as carbides and nitrides of transition metals, along with phonon thermal conductivity, electronic thermal conductivity is also significant: е = (1/ 3) Сve ve lе, where Сve= Sat.e ne/zNa is the heat capacity of a unit volume of electron gas, Sat.e= 3R/2, ve is the speed of electrons with energy close to kEF

Slide 24

Dependence of thermal conductivity on temperature for most ceramics. Relationship between the thermal conductivity of ceramics and its porosity. n=1.5-2 For example, with a porosity of 0.5  decreases by 4 times

Slide 25

Thermal Expansion Characteristics of Ceramics True TELE Average TELE Linear Expansion For Ceramics

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Thermal properties

Fire resistance is the ability to withstand high temperatures without melting. Determined by the temperature at which the pyroscope falls. The most important property of refractories

Slide 27

Heat resistance is the ability of ceramics to withstand temperature fluctuations without collapsing during its operation. Evaluation methods - T= (1-)в/cE For refractories, a direct method for determining heat resistance is used: heating the end of the brick to 850C and 1300C, followed by cooling in running water. Thermal resistance is assessed by the number of heat cycles until the product loses 20% of its weight due to destruction. By loss of mechanical strength during thermal cycling By the limiting value T at which the sample is destroyed

Slide 28

Thermal aging of ceramics An increase in the grain size of the material due to the process of recrystallization during high-temperature operation of products. The grain size can reach hundreds of microns, as a result of which the strength characteristics of ceramics are sharply reduced. The growth of grain size is determined by the formula where D0 is the initial grain size, Q is the activation energy of recrystallization, n=const (for oxides n=1/3),  is the holding time at temperature T,h.

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Lecture 3

Electrophysical and chemical properties of ceramics

Slide 30

Electrophysical properties of ceramics: dielectric constant , temperature coefficient of dielectric constant TK, - specific volume and surface resistance v and s, - dielectric losses tg, - electrical strength or breakdown voltage Upr.

Slide 31

Dielectric constant The ratio of charges Q and capacitances C on the capacitor plates when replacing plates from a given dielectric with a vacuum. Qm – charge of a capacitor with a dielectric plate; Qv is the charge of a capacitor with vacuum. This change in the electrical capacitance of the capacitor occurs as a result of the polarization phenomenon of the dielectric. +++++++++++++++ +++++++++++++++ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Lining Ceramic

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Electronic polarization is an elastic displacement of the center of gravity and deformation of a negatively charged electron cloud under the influence of an electric field. Ionic polarization is the relative displacement of elastically bound ions of different charges. This type of polarization is inherent in all types of ceramics containing crystalline substances of ionic structure. Ionic polarization also occurs instantly. If the return of electrons or ions requires any noticeable period of time, i.e., relaxation occurs over time, then a distinction is made between electron- and ion-relaxation polarization. Spontaneous polarization is an orientation of electrical moments directed in relation to an external electric field, located randomly in individual regions of the crystal (domains) before the application of an electric field. In most oxide, silicate and aluminosilicate ceramic materials,  is 6-12. However, the  of some ceramics reaches several thousand (for example, BaTiO3).

Slide 33

Temperature coefficient of dielectric constant TK. Ceramics with low TK are of greatest value, as they ensure temperature stability of electrical circuits that include a ceramic dielectric.

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Ceramics with low TK are of greatest value, as they ensure temperature stability of electrical circuits that include a ceramic dielectric.

Slide 35

Specific volume and surface resistance vi и s I I S n l d

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Electrical conductivity of ceramics where  is the specific electrical conductivity, q is the charge of the carrier in coulombs; n is the number of carriers per unit volume, =v/E is the mobility of charge carriers, cm2/(sV) In the vast majority of cases, the electrical conductivity of ceramics is ionic in nature. Ions of the glassy phase are more mobile than ions of the crystalline phase. They are the main source of electrical conductivity. Alkali metal ions, especially Na+ and Li+, have high mobility. Therefore, in electrical insulating ceramics the content of alkali oxides should be minimal.

Slide 37

Dependence of electrical conductivity and electrical resistance of oxide ceramics on temperature where 0, 0, are the values ​​of electrical conductivity and volumetric resistivity at 0°C;  – temperature coefficient. With increasing temperature, the electrical conductivity of oxide ceramics increases, since the mobility of ions increases as a result of heating.

Slide 38

Dielectric Losses When a ceramic material is exposed to an electric field, a certain amount of electrical energy is absorbed. This energy expended on the work of moving the structural elements of the crystal lattice is called dielectric losses. Dielectric losses are accompanied by heating of the ceramics, in some cases significant. Dielectric losses are assessed by the dielectric loss angle or the tange of this angle. The dielectric loss angle  is the angle that complements up to 90° the phase shift angle  between current and voltage in a capacitive circuit.

Slide 39

U I j jr ja   As a result of capacitive and active resistance, energy is absorbed by the ceramic capacitor. The absorbed power will be Q = UIcos. In an ideal dielectric =90°, cos90°=0, therefore, Q=0. In real dielectrics  = (90°-). cos(90°-) =sin. ThenQ = UIsin. For small  sintg. So, Q = UItg and tg = I/U = ja/jr. This value (tg ) is used to estimate dielectric losses. Dielectric losses in ceramic dielectrics consist of energy costs for: through electrical conductivity, polarization, and ionization of the gaseous phase.

Slide 40

Dielectric losses associated with end-to-end electrical conductivity can be calculated using the formula tg = (l.81012)/(f), where  is the dielectric constant; f – frequency;  – resistivity. Dielectric losses caused by polarization are most significant in easily polarized types of ceramics that have relaxation polarization. These losses are especially significant in ferroelectric ceramics, which are characterized by spontaneous polarization. Also a source of losses is the gas phase, the ionization of which requires a certain amount of energy. Ceramics with a close-packed crystal structure and a minimum content of the glassy phase have the lowest dielectric losses.

Slide 41

Electrical strength of ceramics

The ability to withstand the action of an electric field. Characterized by breakdown voltage and breakdown voltage. Breakdown voltage allows you to compare the properties of different materials: Epr = Unp/h, where Unp is the breakdown voltage, h is the thickness of the test sample. Breakdown of ceramic material in high-intensity fields can occur through electrical or thermal breakdown. Electrical breakdown is of an electronic nature - an electron avalanche is created and the material loses its electrical insulating ability. Thermal breakdown is the result of a sharp increase in temperature, accompanied by local melting of ceramics under the influence of increased conductivity and dielectric losses.

Slide 42

Radiation resistance of ceramics

The ability to maintain properties under the influence of a certain dose of ionizing radiation (flux of -quanta and neutrons). It is assessed by the integral radiation dose, which does not lead to a change in the properties of ceramics within certain limits, as well as by the radiation dose rate. The integral radiation dose is the product of the neutron flux and the irradiation time (n/cm2). Irradiation power is the magnitude of the neutron flux passing through a unit surface of irradiated ceramics per unit time n/(cm2s). Neutrons are divided according to their energy into thermal (with energy from 0.025 to 1 eV), intermediate (with energy from 1 to several thousand eV) and fast (with energy more than 100 keV).

Slide 43

Neutrons interact with ceramics through the scattering or capture mechanism. There is elastic scattering of neutrons, accompanied only by their loss of kinetic energy, and inelastic, accompanied by the decay of the nucleus with the emission of a secondary neutron and the formation of a stable radioactive recoil nucleus and the emission of gamma quanta. The capture of neutrons causes the decay of the nucleus and is accompanied by the emission of secondary neutrons, protons, - and -particles and nuclear fragments, and the formation of new isotopes. Dispersion and capture are characterized by the cross section "scattering cross section" and the "capture cross section", which express the probability of a given nuclear reaction. The cross section has the dimension of area and is expressed in barns (1 barn = 10-24cm2).

Slide 44

As the cross-section decreases, the likelihood of a reaction decreases.

Slide 45

Changes in the properties of ceramics with an integral irradiation flux of 1020 n/cm2 expansion of the crystal lattice by 0.1-0.3% decrease in density by 0.2-0.5%, increase in porosity phase transitions the thermal conductivity of some types of ceramics decreases by an order of magnitude, heat resistance decreases increase coefficient of linear expansion by 110-6 K-1 due to the disruption of intercrystalline bonds, strength and hardness occur, dielectric losses increase, dielectric constant and breakdown voltage change little. a number of chemical reactions may occur, accompanied by the release of gases (CO, CO2, H2O, O2, He)

Slide 46

Chemical properties of ceramics

The most common cases of chemical interaction between ceramics and other substances are the following: interaction with acids and alkalis - corrosion in solutions. interaction with melts, often metal - corrosion in melts. interaction with gases – gas corrosion.

Slide 47

Corrosion in solutions The study of the corrosion resistance of ceramics in various solutions of acids and alkalis is necessary to assess the possibility of manufacturing from it parts of chemical equipment, pumps for pumping acids, bearings operating in aggressive environments, etc. To assess durability, the loss in mass of a ceramic sample is usually calculated after it is kept in a solution of a given concentration. Often the sample is kept in a boiling solution. The permissible weight loss over a given time for acid-resistant ceramics should not exceed 2–3%.

Slide 48

Corrosion in melts When melting metal in crucibles made of oxide ceramics, it can be restored. Oxide-free ceramics are also used for the manufacture of parts that work in contact with molten metals. The rule for choosing the oxide of the crucible material is: the heat of its formation must be greater than the heat of formation of the oxide of the metal being melted. When oxide-free ceramics interact with molten metals, the formation of chemical compounds, interstitial phases, and intermetallic compounds occurs. Corrosion of ceramics in melts is determined by microscopic, chemical, and phase analysis methods, which make it possible to determine the presence and quantity of interaction products.

Slide 49

Gas corrosion During operation, ceramics must resist the action of gaseous halogens, sulfur dioxide, nitrogen oxides, various hydrocarbons, etc. If the composition of ceramics includes elements with variable valence, then under certain gas environment conditions redox reactions are possible with the formation of more fusible compounds. The effects of gases are especially enhanced in humid environments and at elevated temperatures. The resistance of ceramics against gaseous agents depends on the chemical and phase composition.

Slide 50

Oxide ceramics are not subject to oxidation. Oxide-free ceramics oxidize when heated in air to high temperatures. In real operating conditions of products made from oxide-free ceramics in engines, the corrosive effect of fuel combustion products containing Na, S, V is added to the oxidation process. The oxidizing ability of SO2 is approximately 15 times higher than that of air. Na2SO4 and V2O5 formed during fuel combustion are highly corrosive. However, oxidation of ceramics in some cases leads to an increase in its strength.

Slide 51

Due to the fairly high corrosion resistance of ceramics, it is difficult to assess the degree of its corrosion damage by changes in the mass of samples, the depth of corrosion penetration, the number of corrosion sites, etc., as is done for metals. Therefore, the effect of ceramic corrosion is assessed by changes in its mechanical characteristics. There are still a large number of cases when ceramics enter into one reaction or another with contacting materials. For example, the interaction of ceramics with molten glass during melting, slag, various salt melts, etc. Such a variety of options for the chemical interaction of ceramics with other media does not make it possible to create a unified methodology for assessing the chemical stability of ceramics.

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Traditional uses of ceramics

building ceramics refractories chemical resistant ceramics fine ceramics

Slide 53

Raw materials of traditional ceramics

clayey materials – clays and kaolins; non-plastic materials – quartz, feldspar, chalk, etc. Clays are a mixture of clay minerals, kaolin is a monomineral clay. The most common clay minerals are kaolinite Al2O32SiO22H2O, montmorillonite Al2O34SiO2Na2OnH2O, hydromica (illite) K2OMgO4Al2O37SiO22H2O. It can be seen that the clay minerals are aluminosilicates, in some cases containing oxides of alkali and alkaline earth metals.

Slide 54

All clay minerals have a layered structure similar to that of mica. When clay is mixed with water, the latter enters the interlayer spaces of the clay mineral, and its layers are able to move relative to each other along the water film and be fixed in a new position. This ability of minerals explains the most important property of clay - its plasticity.

Slide 55

Non-plastic materials are divided into so-called thinners, fluxes, organic and special additives. Thinning agents are designed to reduce the plasticity of clays. They can be natural - quartz, quartz sand and artificial - fireclay (fired ground clay). Fluids are used to reduce the sintering temperature and increase the density of the sintered material. The most common fluxes are feldspars, which are aluminosilicates containing oxides of alkali and alkaline earth metals. Organic additives serve to activate the sintering process, as well as to obtain a porous structure; special additives are used to achieve the specified physical and chemical characteristics of the material.

Slide 56

Construction ceramics - wall - facade - ceramics for products for underground communications ceramic fillers Wall materials include, first of all, brick. For its production, low-melting clays are used: hydromicas with admixtures of kaolinite, montmorillonite, hematite, etc. Facade ceramics - facing bricks, facade tiles are made mainly from refractory clays (with a predominance of kaolinite) and some low-melting clays.

Slide 57

The high corrosion resistance of ceramics makes it possible to use products made from it for laying underground communications. Such products include drainage and sewer pipes. Drainage pipes are used to construct drainage networks. For their production, low-melting clays are used, similar to those used in the production of bricks. Ceramic sewer pipes must be dense and chemical resistant. The main raw materials for their production are refractory or refractory clays, as well as mixtures of various clays. Ceramic fillers include expanded clay - a granular expanded material that has the structure of frozen foam at the fracture. Expanded clay is made from hydromica with the addition of iron ore, coal, peat, and fuel oil. The main purpose of additives is to increase the swelling properties of clays during the firing process.

Slide 58

Fine ceramics Divided into porcelain and earthenware. Porcelain is made from a fine mixture of kaolin and fire clay (20–65%), quartz (9–40%) and feldspar (18–52%). Porcelain structure: glass phase (up to 60%) crystalline phase - mullite 3Al2O32SiO2 (up to 25%). Porosity is 3–5%. Porcelain products are usually glazed. Porcelain is used for the manufacture of chemically resistant tableware and electrical insulators for various purposes (electric porcelain).

Slide 59

Earthenware differs from porcelain in its greater porosity (up to 14%), low physical and mechanical characteristics, and therefore its use in technology is limited. The structure of faience is represented by grains of dehydrated clayey matter and quartz, cemented by a small amount of glassy phase, which is formed by the interaction of fluxes with clay, kaolin, and quartz. Products for household, sanitary and technical purposes, as well as facing tiles are made from faience.

Slide 60

Refractories Materials and products that can withstand mechanical and physical-chemical influences at high temperatures and are used for laying various heating units. Types of refractories: silica aluminosilicate magnesia Siliceous refractories include silica and quartz ceramics. The main component in them is silica SiO2.

Slide 61

Dinas contains at least 93% SiO2 in the form of tridymite (up to 70%) or cristobalite. Dinas is obtained from quartzites, less often from quartz sand. Fire resistance up to 1710–1730°C, high heat resistance, resistance to acidic melts. It is used for laying vaults and walls of open-hearth and glass furnaces. Quartz ceramics is a white amorphous material consisting of sintered grains of quartz glass, has fire resistance up to 2200°C (short-term), extremely high heat resistance (t over 1000°C) due to low LCTE. It is used as a refractory in metallurgy and the glass industry. As technical ceramics - in rocket technology for the manufacture of antenna radomes.

Slide 62

Aluminosilicate refractories are produced on the basis of a two-component Al2O3-SiO2 system. Main types: fireclay and high-alumina Fireclay refractories contain 28-45% Al2O3. Made from refractory clays and kaolins and fireclay (40-85%). They have a fire resistance of 1580–1750°C and are used for laying most heating units. High alumina refractories contain more than 45% Al2O3. As a result, these materials have increased physical and mechanical properties and fire resistance up to 2000°C. High-alumina products are used for laying blast furnaces.

Slide 63

Magnesia refractories are divided into magnesite and dolomite. Magnesite refractories consist of the mineral periclase MgO. Their fire resistance exceeds 2000°C. Used in the steelmaking industry. The raw material for their production is magnesite MgCO3. Dolomite refractories are produced by sintering a mixture of dolomite CaCO3MgCO3 and quartzites. They have fire resistance up to 1780°C, are characterized by a long service life and are used for laying open-hearth and rotary furnaces.

Slide 64

General scheme of traditional ceramics technology Obtaining raw materials Forming products Drying Firing (sintering)

Slide 65

Obtaining and preparing starting materials Traditional ceramics technology uses natural raw materials (clays, feldspar, sands) subjected to appropriate processing. Processing includes grinding and mixing the components. Clay materials are processed in clay cutting machines, dried and then crushed in disintegrators. The wastes and driftwood are crushed in crushers, ball and vibrating mills. After grinding, the powders are sifted to obtain the desired fractions. The components of the charge must be thoroughly mixed and have the required degree of moisture.

Slide 66

Molding The method of semi-dry pressing and methods of molding plastic masses are used. Pressing is carried out on presses of various designs in metal molds or on installations for hydrostatic pressing. In the first case, high productivity of the process is achieved, in the second - the possibility of obtaining uniformly dense products of complex configurations. Semi-dry pressing is used in the technology of refractories, wall ceramics, and electroporcelain.

Slide 67

Plastic molding is most common in traditional ceramic technology. Plastic molding methods: extrusion (extrusion), stamping and turning. In all methods, the raw material contains water in an amount of 30–50 vol. %. Extrusion is carried out on continuous presses through profile mouthpieces. This method is used in the production of bricks, pipes, as well as some technical ceramics products (rods, tubes). Stamping is used to produce products with more accurate dimensions and a good surface. Refractories and acid-resistant bricks are formed in this way. The turning method is used in the production of porcelain and earthenware.

Slide 68

In the production of traditional ceramics, an important operation is the drying of molded products, since they contain a significant amount of temporary binder (up to 25%). Drying occurs in tunnel dryers with air, gas or steam-air coolant. The moisture content after drying does not exceed 1–3%. Drying time, depending on the type of product, can range from 6 minutes to several days.

Slide 69

Firing is the defining operation in ceramic technology. During firing, the following processes occur: - sintering of pressed particles - shrinkage or growth of the product - polymorphic transformations - chemical reactions - glass formation - crystallization The driving force for sintering is excess surface energy at the interface of the powder system. The following types of sintering are distinguished: liquid-phase and solid-phase.

Slide 70

During solid-phase sintering, substance transfer occurs due to the diffusion of crystal lattice defects, mainly vacancies. The contour of the particle contact site is a source of vacancies due to their increased concentration, and the contact surface itself and the convex surfaces of the particles are a sink. The main signs of ceramic sintering are an increase in the density and mechanical strength of the product. In liquid-phase sintering, compaction occurs due to the surface tension forces of the resulting liquid phase.

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Model of solid-phase sintering of particles x y

Slide 72

Model of liquid-phase sintering of particles x y The liquid phase does not dissolve the solid The liquid phase dissolves the solid. f. TV f. TV f. TV f. TV f. and. f.

Slide 73

Technical ceramics

The class of technical ceramics unites a large number of ceramic materials that differ both in chemical composition and purpose. At the same time, there are features common to all technical ceramics, which fundamentally distinguish them from traditional types of ceramics: 1. The use of mainly, and for some ceramics exclusively, synthesized raw materials (powders). 2. Application of new technologies (PM, HIP, GP, GIP, etc.) The properties of technical ceramics depend decisively on the technology for obtaining raw materials, compacting and sintering of products. Therefore, materials of the same chemical composition, but obtained by different methods, can have qualitatively different levels of physicochemical and mechanical characteristics and a wide variety of applications.

Slide 74

Ceramics based on silicates and aluminosilicates

The basis is double or triple silicates or aluminosilicates of the MgO-Al2O3-SiO2 system. There are four such compounds in this system: 1. ZAl2O3 2SiO2 - mullite, 2. MgO SiO2 - clinoenstatite, 3. 2MgO SiO2 - forsterite, 4. MgO 2Al2O3 5SiO2 - cordierite. Ceramics are called accordingly: mullite, mullite-corundum, clinoenstatite (steatite), forsterite, cordierite.

Slide 75

Mullite and mullite-corundum ceramics (high alumina)

The basis is mullite ZAl2O3 2SiO2 and corundum α-Al2O3. The content of α-Al2O3 is from 45 to 100%. 3 groups: Mullite-siliceous (45-70% Al2O3). 2. Mullite-corundum (70-95% Al2O3). 3. Corundum (95-100% Al2O3).

Slide 76

High alumina ceramic technology

Raw materials: - minerals andalusite, kyanite, kaolin, - additives of technical alumina and electrocorundum. Mullite-silica ceramics are obtained from natural raw materials without enrichment with Al2O3. To obtain mullite and mullite-corundum ceramics, preliminary synthesis of mullite in the form of a briquette or sinter is required. A distinction is made between the synthesis of: primary mullite by transformation of kaolinite or other clay minerals at t1200°C. This mullite makes up the bulk of ceramics. secondary mullite interaction of introduced Al2O3 with silica released during heating at t = 1300–1600°C. It is impossible to distinguish between these types of mullite in a fired product.

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Sintered mullite is ground in ball mills, followed by product forming operations: plastic molding, hot injection molding, pressing. This is followed by sintering of the molded products at a temperature of 1350–1450°C. To reduce the sintering temperature of the mass, additives are usually introduced in the form of marble, dolomite, magnesite, talc, barium carbonate and other substances. When producing mullite-corundum ceramics, 10–15% of pre-burnt alumina must be added to the charge, wet grinding is carried out, then molding and sintering are carried out.

Slide 78

Properties and applications of high alumina ceramics

The mechanical properties of sintered high-alumina ceramics increase with increasing content of Al2O3 and crystalline phases. bend200MPa, E250GPa, HV=1000-2000.  mullite-siliceous ceramics 5.5-6.5, mullite-corundum 6.5-9, corundum 10.5-12 v depends on the phase composition of the ceramics and the amount and composition of the glassy phase, increases with increasing Al2O3 content. tg increase with increasing content of the glassy phase. Epr=30-35kW/mm. Main applications: - vacuum technology, - insulators for spark plugs of internal combustion engines, - parts of electrical and radio equipment.

Slide 79

Clinoenstatite ceramics

The base is magnesium metasilicate MgO·SiO2 – clinoenstatite. The raw material is the mineral talc - hydrous magnesium silicate. Dense varieties of talc are called steatite. Therefore, clinoenstatite ceramics are often called steatite or simply steatite. Clinoenstatite exists in three modifications: enstatite at 1100-1260°C irreversibly turns into protoenstatite; upon cooling, protoenstatite at 800-1000°C turns into clinoenstatite. When the transition of protoenstatite to clinoenstatite is incomplete, volumetric changes in ceramics occur in products (up to 6%), which lead to degradation of mechanical and electrical properties - aging of steatite occurs. It is necessary to increase the viscosity of the glassy phase, which inhibits the growth of protoenstatite crystals.

Slide 80

Technology, properties and application of clinoenstatite ceramics

dehydration of talc at 850–1300°C, mixing and wet grinding of components in ball mills, dehydration of the mass on a filter press to a moisture content of 18–22%, production of blanks on vacuum presses, plastic molding: turning on lathes, modeling in plaster molds, extrusion, etc. Dry pressing, stamping, and hot casting of thermoplastic slips are also used. sintering at 1170–1340°C, depending on the composition, in electric furnaces with silicon carbide heaters. Has low tg, high Epr. It is used as a high-frequency dielectric, an insulator for electric vacuum equipment, and in high-voltage technology.

Slide 81

Forsterite and cordierite ceramics

Forsterite is a ceramic based on magnesium orthosilicate 2МgО·SiO2 – forsterite. Advantage - due to the absence of polymorphic transformations, it is not subject to aging. Ceramics based on cordierite 2МgО·2Аl2О3·5SiO2 are called cordierite. Composition of cordierite in mass%: MgO-13.7; Al2O3-34.9; SiO2- 51.4. Raw materials - talc, refractory clays, technical alumina. Products made of forsterite and cordierite are formed by hot casting, pressing, extrusion, and stamping. The sintering temperature for forsterite ceramics is 1220–1380°C, for cordierite ceramics - 1300–1410°C. To expand the sintering range of cordierite, it is recommended to introduce 2–4% alkali metal oxides.

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Properties and applications of forsterite and cordierite ceramics

Dense sintered forsterite ceramics have high electrophysical characteristics. Due to its high linear expansion coefficient, forsterite ceramics are used in electric vacuum technology as an insulator in contact with metals, mainly titanium. Sintered cordierite ceramics have a very low coefficient of thermal expansion and, as a result, high heat resistance. This allows it to be used for the manufacture of arc chutes in high-voltage switches, as well as for the manufacture of heat-resistant cookware.

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Other types of aluminosilicate and silicate ceramics

Celsian ceramics The basis is barium aluminosilicate BaO2·Al2O3·2SiO2 – Celsian. Celsian crystallizes in the monoclinic system. At temperatures above 1100°C it transforms into a hexagonal modification. Technology: - synthesis of celsian in a briquette at t=1250-1300°C, grinding and crushing. - powder plasticization, pressing. - sintering at t=1380-1400°C in slightly oxidizing and neutral environments. Celsian ceramics have low tg, high v and low LCTE. Thanks to these properties, Celsian ceramics are used for the manufacture of certain radio components.

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Lithium ceramics The basis is lithium aluminosilicates, mainly spodumene Li2O·Al2O3·4SiO2. Products can be produced using almost all methods of ceramic technology. The temperature for the synthesis of lithium ceramics and sintering of products is 1200-1250°C. Lithium ceramics has a low, and some of its compositions have a negative LCTE up to 700°C, which determines its good heat resistance. Also, lithium ceramics has fairly high electrical insulating properties, due to which it is used in the production of certain types of products for radio engineering that operate under conditions of elevated or variable temperatures, as well as other products, such as air heaters, that operate under conditions of sudden temperature changes.

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Wollastonite ceramics The basis is the natural mineral wollastonite - calcium metasilicate CaO·SiO2. Technology. - plasticization of masses with a small amount of clay and fluxing additives. - pressing. - sintering at t=1200–1300°C. Shrinkage is small, which makes it possible to produce products with precise dimensions. Wollastonite ceramics made from pure varieties of natural wollastonite have a high level of electrical characteristics and good heat resistance.

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Al2O3-based ceramics A chemical compound with an ionic-covalent type of bond in the crystal lattice. It has α-, β- and γ-modifications of alumina, and α- and γ-Al2O3 are pure aluminum oxide, and the β-modification is a compound of aluminum oxide with alkali and alkaline earth oxides. In nature, only α-Al2O3 is found in the form of the minerals corundum, ruby, and sapphire, which crystallizes in the trigonal system. Cubic γ- and hexagonal β-Al2O3 are unstable modifications that, when heated above 1500°C, transform into α-Al2O3. Corundum technical ceramics is ceramics containing more than 95% α-Al2O3. In the literature there are private names for corundum ceramics: alumina, corundiz, sinoxol, minalund, M-7, 22ХС, microlite, sapphirite, polycor, etc.

Slide 87

Source materials 1. Alumina. It is obtained by decomposing the mineral bauxite, which is a mixture of aluminum hydroxides, with a solution of caustic alkali to form sodium aluminate, which goes into solution. NaAlO2+2H2O=Al(OH)3+NaOH. Aluminum hydroxide is calcined at a temperature of 1150–1200°C. As a result, technical alumina powder is formed. The resulting powders are spherical (spherulite) agglomerates of γ-Al2O3 crystals less than 0.1 µm in size. The average size of spherulites is 40–70 µm. 2. Electromelted corundum. White electrocorundum (corrax, alundum) is produced by melting technical alumina in electric arc furnaces. The content of α-Al2O3 in white electrocorundum is 98% or more.

Slide 88

To obtain ultradisperse Al2O3 powders, which are used in the technology of structural and instrumental ceramics, methods of co-precipitation of hydroxides (COP) and plasma-chemical synthesis (PCS) have become widespread. The essence of the SOG method is the dissolution of aluminum salts, for example AlCl3, in an ammonia solution and the subsequent precipitation of the resulting hydrates. The process is carried out at low temperatures and long holding times. The resulting hydroxides are dried and calcined, resulting in the formation of Al2O3 powder with a particle size of 10–100 nm. In PCS technology, an aqueous solution of Al(NO3)3 is fed into the plasmatron nozzle. Extremely high temperature gradients arise in the drops of the solution, and a very rapid process of synthesis and crystallization of Al2O3 occurs. The powder particles have a spherical shape and a size of 0.1–1 μm.

Slide 89

Before molding, Al2O3 powders are calcined at a temperature of 1500°C in order to dehydrate and convert them into a stable and denser α-modification. Then alumina and electrocorundum are crushed to particles of 1–2 μm in size in ball and vibration mills. The molding of corundum products is carried out by casting from aqueous suspensions, injection molding, uniaxial static pressing, hydrostatic pressing, hot pressing. Aluminous slips liquefy in both acidic and alkaline environments, and there are certain pH ranges that correspond to the greatest liquefaction. Before casting, the prepared slip is evacuated at a residual pressure of 15–20 mm Hg. Products are cast in plaster molds. The cast products are dried at room temperature. Casting is used to form thin-walled corundum products of complex shapes that do not experience significant mechanical stress during operation.

Slide 90

To form products from Al2O3 of simple shape, for example, bushings, cutting inserts, nozzles, dies, uniaxial static pressing in metal molds is used. In this case, a plasticizer, most often rubber, is added to the powder in an amount of 1–2% wt. The hydrostatic pressing method makes it possible to obtain large-sized ceramic blanks of complex shapes. The uniform distribution of density in the compact has a beneficial effect on the uniformity of shrinkage during sintering. The most durable products from Al2O3 are produced by hot pressing (HP) in graphite molds coated with BN and hot isostatic pressing (HIP) in gasostats. In this case, compaction of the powder into the product and sintering occurs simultaneously. The pressing pressure is 20–40 MPa, the sintering temperature is 1200–1300°C. GP and GIP methods are technologically complex and energy-intensive.

Slide 91

Sintering of corundum ceramics in most cases is solid-phase. The sintering temperature depends on the dispersion and activity of the initial powders, sintering conditions, and the type and amount of additives. The maximum particle size of Al2O3 powder should not exceed 3–5 µm. The sintering temperature is in the range of 1700–1850°C. Ultra- and nanodispersed Al2O3 powders, as a result of high surface energy and defectiveness, can be sintered to a high density (0.95) at a temperature of 1600°C. In many cases, various additives are introduced into the corundum charge. The addition of TiO2 reduces the sintering temperature of corundum to 1500–1550°C. In this case, a solid solution of TiO2 in Al2O3 is formed, which causes distortion of the corundum crystal lattice, active sintering and recrystallization. The addition of 0.5–1% MgO inhibits recrystallization: the size of the sintered ceramic crystals does not exceed 2–10 μm. The fine-grained structure of corundum with the addition of MgO improves the mechanical properties of corundum. A decrease in the sintering temperature of corundum with the introduction of MgO is not observed.

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Properties of corundum ceramics

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Traditional areas of application of corundum ceramics: refractory, chemical industry, electrical and radio engineering. With the advent of new technologies for producing initial powders, molding and sintering products, the scope of application of corundum ceramics has expanded significantly. Currently, high-strength ceramics based on Al2O3 are used for the manufacture of structural products used in mechanical engineering, aviation and space technology. Corundum is the main material in mineral ceramic technology, which is used for finishing cast iron and some steels. The basis of mineral ceramics is Al2O3 or its mixture with carbides, nitrides, etc.

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Physico-mechanical properties of instrumental ceramics based on Al2O3

Slide 95

Ceramics based on zirconium dioxide A feature of zirconium dioxide is its polymorphism. Pure ZrO2 is in the monoclinic phase at room temperature and undergoes phase transformations when heated. The t-ZrO2↔c-ZrO2 transition is of a diffusion nature and plays a very important role in the production of so-called partially stabilized zirconium dioxide. The m-ZrO2↔t-ZrO2 transformation proceeds according to the martensitic mechanism and is accompanied by volumetric changes of 5–9%. Therefore, it is impossible to obtain compact products from pure ZrO2.

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To increase the stability of the t-phase, additives of stabilizer oxides are introduced into ZrO2: MgO, CaO, Y2O3 Fig. 5. State diagram of the ZrO2-Y2O3 system: T0 – transition temperature m-ZrO2↔t-ZrO2

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In addition to the formation of solid solutions based on ZrO2, another method is used to stabilize the high-temperature modification t-ZrO2 in a hard corundum matrix.

Slide 98

The effect of transformation hardening of zirconium ceramics is realized when the sintered material contains t-ZrO2 particles that can transform into m-ZrO2. Cracks that appear during loading propagate in the material until t-ZrO2 particles appear in their front. Such a particle, located in a compressed state (in a corundum matrix) or in a coherently bound state with the matrix (if c-ZrO2 predominates in the composition of the material), is resistant to the t→m transition even at low temperatures. Once in the stress field at the tip of a propagating crack, the particle receives energy sufficient for transformation. Thus, the energy of the propagating crack turns into the energy of the t→m transition and the catastrophic growth of the crack stops.

Slide 99

Crack t-ZrO2 t-ZrO2→m-ZrO2 Matrix (-Al2O3, c-ZrO2, etc.) Scheme of transformation hardening of zirconium ceramics

Slide 100

Main types of structures of zirconium ceramics: a – CSZ, b – ZTA, c – PSZ, d – TZP

Slide 101

1. Stabilized zirconia CSZ: cubic solid solution based on ZrO2. To sell this material, the amount of additive MgO, CaO must be more than 15–20 mol.%, Y2O3 - more than 10 mol.%. CSZ has low strength characteristics: σ bend no more than 250 MPa and K1s up to 3 MPa/m0.5 and is used as a refractory material, as well as in solid electrolyte technology. 2. Ceramics strengthened with zirconium dioxide ZTC (Zirconia Toughened Ceramic): dispersed t-ZrO2 particles are distributed in the ceramic matrix and are stabilized by compressive stresses. The most technically important compositions are Al2O3-ZrO2 (ZTA: Zirconia Toughened Alumina), which are used primarily as tool materials. Optimal mechanical characteristics are achieved with a ZrO2 content of about 15 vol.%: σben up to 1000 MPa and K1s up to 7 MPa/m0.5.

Slide 102

3. Partially stabilized zirconium dioxide PSZ (Partially Stabilized Zirconia). It is formed by adding oxides Mg, Ca, Y, etc. to ZrO2. During sintering in the homogeneity region of the cubic phase, large c-ZrO2 grains (60 µm) are formed. After annealing, tetragonal particles appear in the two-phase region, coherently associated with the cubic phase. In ZrO2-MgO(CaO) systems, the t-particle size should be less than 0.25 µm. The volume content of the t-phase is about 40%. PSZ has K1c up to 10MPa/m0.5 and σbend up to 1500MPa. 4. Tetragonal Zirconia Policrystals (TZP). This material is sold in ZrO2–Y2O3 systems. Sintering occurs in the region of homogeneity of the t-phase, followed by quenching. TZP has a σben of up to 2400 MPa with K1s of about 15 MPa/m0.5, and is used in the production of products for structural and instrumental purposes.

Slide 103

Zirconium ceramic technology Pre-grinding UDP to crush microspheres. Forming of ZrO2 powders by uniaxial static pressing and pressing in hydrostats at a pressure of 400–600 MPa. Sintering at a temperature of 1500–2000°C, depending on the type and amount of stabilizer oxide. Heat treatment - annealing at 1400–1500°C in order to isolate strengthening dispersed inclusions of the t-phase. When manufacturing products from tetragonal ZrO2, hardening is used at a sintering temperature of 1600°C. Products made of ZrO2 produced by the GP and HIP methods have the highest strength characteristics.

Slide 104

Applications of Zirconium Ceramics Traditionally, ZrO2-based ceramics have been used in the metallurgical industry to make crucibles for melting metals. Today, zirconium ceramics is one of the most promising ceramic materials for structural and instrumental purposes and is used in the technology of producing parts for gas turbine and diesel engines, friction units, pump sealing rings, shut-off valve elements, spray chamber nozzles, wire drawing dies, and cutting tools. ZrO2-based ceramics are also used in medicine for the manufacture of implants in bone tissue.

Slide 105

Oxide-free technical ceramics Oxide-free ceramics are polycrystalline materials based on compounds of non-metals of groups III–VI of the periodic system of elements, excluding oxygen, together with transition metals that have unfinished electronic layers. Based on their crystal structure, oxide-free ceramics form two main classes: 1. Metal ceramics: compounds of the above nonmetals with transition metals, having an interstitial phase structure. 2. Non-metallic ceramics: compounds of B, C, N, Si, chalcogens (except O) with each other, as well as with some transition metals. They have a complex crystal structure with a covalent type of interatomic bond.

Slide 106

Metal ceramics Carbides and nitrides Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W. The condition for the formation of the interstitial phase is determined by Hagg’s rule: rX:rMe

Slide 107

The difference between interstitial phases and solid solutions is that the latter are formed at significantly lower concentrations of carbon and nitrogen, for example, ferrite and austenite, and have a metal crystal lattice, while interstitial phases form a lattice different from the metal lattice. In this sense, the incorporation phases can be considered a type of chemical compound. At the same time, interstitial phases have wide areas of homogeneity; for example, TiC can contain from 20 to 50 mol%. carbon, which is not typical for chemical compounds.

Slide 108

Transition metal carbides The most widely used in industry are WC, TiC, TaC and ZrC. Interest in these materials is due to their very high hardness (from 20 to 35 GPa), which they retain up to temperatures above 1000°C. Reasons for the high hardness of carbides: The metals that form carbides have very high melting points and are low in plasticity, i.e. the forces of interatomic bonds of these metals are very high. 2. Inhibition of dislocations by carbon atoms and reduction of plasticity. For example, in the fcc lattice of TiC and TaC, carbon atoms are located parallel to the (111) slip planes, in the hcp lattice of WC - parallel to (001). With high hardness, carbides are quite brittle.

Slide 109

Transition metal carbides do not exist in nature, so the first stage in their technology is synthesis. Carbide powders are obtained either by direct synthesis of carbon and metal according to the formula Me+C→MeC, or by the reduction of the metal from the oxide with simultaneous carbidization. The second method is preferable, because oxides of the corresponding metals are much cheaper than powders of pure metals.

Slide 110

In general, the process of obtaining carbide powders occurs according to the following scheme: the oxide powder of the corresponding metal is mixed with soot or crushed coke and heated to the temperature at which carbidization occurs. For example, for titanium carbide the process occurs according to the reaction: t=2100-2300°C TiO2+3C=TiC+2CO. The resulting powders are crushed, sifted, mixed with the necessary components, pressed into products that are sintered at appropriate temperatures.

Slide 111

In their pure form, the carbides in question find very limited use. This is primarily due to technological problems in producing compact products; for example, in order to sinter a product from TiC, which has a melting point of 3200°C, a sintering temperature of at least 2500°C is required. Secondly, as already noted, pure carbides are very fragile. Transition metal carbides are mainly used in tool production as part of hard alloys. Standard grades of hard alloys are made on the basis of tungsten, titanium, and tantalum carbides. Cobalt, nickel, and molybdenum are used as binders. Hard alloys are produced using powder metallurgy methods by liquid-phase sintering.

Slide 112

Slide 113

Tungsten-free hard alloys BVTS Marking: carbide former (B - tungsten, T - titanium, second letter T - tantalum), binder (K ​​- cobalt). The mass percentage of the binder is the last number. In two-carbide and three-carbide alloys, the number in the middle indicates the mass percentage of titanium and tantalum carbides. In BVTS, the figure shows the total mass percentage of the Ni+Mo binder.

Slide 114

Hard alloys are produced in the form of plates: brazed (glued), multifaceted, dies, dies, etc. Multifaceted plates are produced both from standard grades of hard alloys, and from the same alloys with single-layer or multilayer superhard coatings of TiC, TiN, etc. Plates with coatings they have increased durability. To the designation of plates made of standard grades of hard alloys coated with titanium nitrides, the marking of the letters KIB (condensation ion bombardment coating method) is added. Also, the carbides under consideration are widely used as a material for applying corrosion- and wear-resistant coatings to parts. For example, TiC coatings are used to protect equipment surfaces in the chemical industry, and WC coatings are applied to ship propeller shafts.

Slide 115

Transition metal nitrides Of all the transition metal nitrides, TiN and ZrN are most widely used in technology. Just like carbides, nitrides have very high melting points. The hardness of nitrides is somewhat inferior to that of carbides; for example, ZrN has a microhardness of about 25 GPa. The reason for the high hardness of nitrides, as well as carbides, is due to the structural features of the interstitial phases. Nitrides are synthetic substances. Nitride powders are obtained by direct synthesis of metal with nitrogen by nitriding metal powders at appropriate temperatures: 2Me+N2→2MeN. Nitrides are also obtained by reacting metals with ammonia and other methods, including vapor deposition.

Slide 116

Transition metal nitrides are mainly used as additives to special alloys, as well as materials for applying wear-resistant coatings. In tool production, the method of ion-plasma sputtering of TiN and (Zr,Hf)N coatings on a variety of cutting tools has become very widespread. ZrN is used to coat the electrodes of internal combustion engine spark plugs to improve their performance characteristics. TiN and ZrN plates are used in rocket technology to protect rocket bodies and spacecraft.

Slide 117

Non-metallic oxide-free ceramics Non-metallic oxide-free ceramics include materials based on borides ZrB2, CrB2, TiB2, carbides B4C, SiC and some transition metals, nitrides BN, Si3N4, AlN, silicides, phosphides, arsenides and chalcogenides (except oxides). Ceramics based on phosphides, arsenides and chalcogenides are not considered in the course due to their limited use in modern mechanical engineering. The most promising ceramics for structural applications are those based on SiC, Si3N4 and AlN - compounds with a large proportion of covalent bonds, the crystals of which are characterized by significant Peierls stresses. In such crystals, the movement of dislocations is difficult, so these compounds retain their strength up to very high temperatures.

Slide 118

The most appropriate is the use of SiC, Si3N4 and AlN instead of metals in engine building. This is due to the fact that making the flow part of a gas turbine engine (GTE) from ceramics and increasing its operating temperature to 1400°C and higher will increase the efficiency from 26 to 45%. By using ceramics in a diesel engine, it can be made uncooled, reducing weight and increasing efficiency. The feasibility of using ceramics for engine construction is explained not only by its high heat resistance, but also by the fact that, due to its higher corrosion resistance compared to metals, low-grade fuel can be used. The use of ceramics for the manufacture of engine parts reduces their cost, which is due to the low cost of ceramics compared to Ni, Cr, Co, Nb, etc.

Slide 119

SiC-based ceramics Silicon carbide (carborundum) SiC is the only compound of silicon and carbon. This material is extremely rare in nature. It exists in two modifications: polytypic hexagonal α-modification (about 20 structures), cubic β. The β-SiC→α-SiC transition occurs at approximately 2100°C. Above 2600–2700°C α-SiC sublimes. Pure SiC of stoichiometric composition is colorless. When the silicon content is exceeded, SiC turns green and carbon turns black. Properties of SiC: Hμ up to 45 GPa, σben up to 700 MPa, Тр2000°С. At room temperature, the destruction of SiC is transgranular and has the character of cleavage. At 1050°C, the nature of the destruction becomes intercrystalline.

Slide 120

SiC is resistant to all acids, with the exception of HF and HF+HNO3. SiC is less resistant to alkalis. It has been established that SiC is wetted by iron group metals and manganese. In the manufacture of abrasive, refractory products and electric heaters from SiC, the starting materials are silica (quartz sand) and coke. They are heated to high temperatures in electric furnaces, carrying out the synthesis using the Acheson method: SiO2+3C=SiC+2CO2. Around the heating element (core) there is a zone of the synthesized product, and behind it there are zones of low-purity crystals and unreacted components. The products obtained in the furnace are separated into these zones, crushed, processed and obtained as a general purpose silicon carbide powder. The disadvantage of these SiC powders is their high contamination with impurities.

Slide 121

To obtain structural ceramics, it is necessary to use high-purity, homogeneous, highly dispersed SiC powders, which are obtained by the synthesis method: The original metallurgical Si is crushed and ground, washed from impurities in acid, and ground. The synthesis of SiC is carried out in a reactor by feeding Si into special nozzles, gas - propane: t>1100°C 3Si+C3H8=3SiC+4H2. Products made of SiC are molded by pressing, extrusion, and injection molding. Silicon carbide ceramic technology usually uses hot pressing, reaction and activated sintering.

Slide 122

The GP method makes it possible to obtain high-strength SiC-based ceramics. Pressing is usually carried out in molds made of graphite or boron nitride at pressures of 10-50 MPa and temperatures of 1700-2000 ° C. GP makes it possible to obtain only products of fairly simple shapes and relatively small sizes. Products of complex shapes with high density are produced by hot isostatic pressing (HIP). The activated sintering method allows SiC to be sintered to a density of over 90% thanks to the additions of B, C, Al, due to the formation of a diffusion layer on the surface of the particles.

Slide 123

The reaction sintering method allows the process to be carried out at lower temperatures and to obtain products of complex shapes. To obtain the so-called “self-bonded” silicon carbide, compacts of SiC and carbon are sintered in the presence of silicon. In this case, secondary SiC is formed and SiC recrystallizes through the silicon melt. As a result, non-porous materials are formed containing 5–15% free silicon in a silicon carbide matrix. Reaction sintering is an economical process due to the use of inexpensive thermal equipment, the sintering temperature is reduced from the commonly used 1600–2000°C to 1100–1300°C.

Slide 124

The reaction sintering method is used in the production of silicon carbide heating elements. SiC is a thermistor, i.e. it changes resistance under the influence of temperature. Black SiC has high resistance at room temperature and a negative temperature coefficient of resistance. Green SiC has a low initial resistance and a slightly negative temperature coefficient, which becomes positive at temperatures of 500–800°C. Silicon carbide heating elements (SCH) are usually a rod or tube that has a middle working part with a relatively high electrical resistance (“hot” zone) and output (“cold”) ends with a lower electrical resistance that do not heat up during operation of the furnace.

Slide 125

The industry produces two types of heating elements made of SiC: 1. Carborundum. They have a working rod and two separate shorter contact leads in the form of carborundum rods impregnated with metal. 2. Silite. Heaters with thickened outlet ends (cuffs). Composite carborundum heaters are formed from coarse-grained green SiC powder with the addition of carbon black (1.5%) and liquid glass, then fired in a backfill of coal-sand mixture at a temperature of about 2000°C. The heater is pre-coated with a conductive paste consisting of coke, graphite and quartz sand. The product is sintered by direct electrothermal heating in special furnaces by passing a current of 80–100 AV through the workpiece for 40–50 minutes.

Slide 126

Silite heaters are extruded from a mixture of fine-grained SiC, carbon black (20%) and phenol-formaldehyde resin. The working part and cuffs are formed separately. The composition of the cuff part is designed for high conductivity and contains about 40% Si. When silite heaters are sintered, the carbon and silicon present in the mass are converted into “secondary” SiC through the reaction sintering mechanism. A mixture of ground sand, petroleum coke and silicon carbide is used as backfill. This mixture, at a temperature of 1800–2000°C, releases vaporous silicon and CO, which penetrate into the workpiece and react with solid Si and C. At the same time, secondary silicon carbide is synthesized by reacting the silicon contained in the charge with carbon.

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Materials based on SiC began to be used much earlier than materials based on Si3N4, AlN, B4C and BN. Already in the 20s, silicon carbide refractories with a silicon dioxide binder (90% SiC + 10% SiO2) were used, and in the 50s, rocket nozzles were made from silicon carbide with a silicon nitride binder (75% SiC + 25% Si3N4). Currently, ceramics based on silicon carbide are used for the manufacture of sealing rings for pumps, compressors, mixers, bearings and shaft sleeves, dosing and control valves for corrosive and abrasive media, engine parts, and metal pipelines for liquid metals. New composite materials with a silicon carbide matrix have been developed.

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The history of the appearance of ceramics. Ceramics appeared 12-15 thousand years ago, back in the Stone Age. The vessels were molded by hand. Crushed shells and crushed granite were added to the clay so that it would not crack during firing. Products were fired at fires. Later, special ovens appeared. In the Copper Age (4 - 6 thousand years ago), the shapes of vessels became diverse, sculptures of people and animals appeared. Products begin to be decorated with ornaments. At first, patterns were extruded with a stamp and a point into wet clay, then they learned how to make paintings with colored clays. The drawings depicted natural phenomena (lightning, moon, sun, water) using conventional symbols. People believed in the magical (witchcraft) power of these signs. Gradually, the original meaning of the ornaments was forgotten, and they began to be made simply for decoration.

Slide 4 from the presentation “Pottery Art”

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Art history

“Hairstyles” - XIX century). Long golden locks fell to her hips. The era of the European Middle Ages (V-XIV centuries). The great French bourgeois revolution marked the end of the age of “vain marquises.” Curls were a must. Hairdressing art has received a new development. Sometimes eyebrows were also shaved off. Young girls wore their hair loose.

“Garden Art” - Basic styles in landscaping. China. Landscape art of England in the second half of the 18th century. Catherine Park. Landscape art of China and Japan. French gardening art of the 17th century. Ancient Greece. Yellowstone Park. Renaissance. Japan. Villa Lante. France. Sacred groves? heroons Philosophical gardens Privately owned gardens.

"Eras of Culture" - Cubism. Epochs of world culture. Surrealism. Romanticism. Neoclassicism. Modernism. Mannerism. Northern Renaissance. Renaissance. Impressionism. Rococo. High Renaissance. Cultural eras. Early Renaissance. Vanguard. Baroque. Epochs. Dadaism. Post-Impressionism.

"Architecture and painting of Germany and the Netherlands" - Old Church of Delft. Architecture. Architecture of the Netherlands. Dutch painting. Architecture and painting of Germany and the Netherlands. Painting of the altar of the Church of St. Bavo. Scandinavia. Four horsemen. Frans Hals. Architecture of Germany. Albrecht Durer. Painting by Dutch masters. Painting by German masters.

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• The term “ceramics” comes from the Greek word “keramos”, which means clay.
• Ceramic products are products made from clay with various additives and fired to a stone state.
• From ancient times to the present day, ceramic products have occupied one of the leading places in the decorative and applied arts of all peoples of the world.

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• The technological scheme for the production of ceramic tiles includes the following main phases:

1. Preparation of slip;
2. Product molding;
3. Drying;
4. Preparation of glaze and glazing (enamelling);
5. Burning.

• Raw materials for ceramic masses are divided into plastic (clays and kaolins) and non-plastic. Additions of fireclay and quartz reduce product shrinkage and the likelihood of cracking at the molding stage. Lead and borax are used as glass formers.

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• The preparation of slip takes place in three phases:
  • First phase: grinding of feldspar and sand (grinding lasts from 10 to 12 hours);
  • In the first phase, clay is added;
  • Kaolin is added to the second phase. The finished slip is poured into containers and aged.
• Transportation from the raw materials warehouse is carried out using a loader to the receiving bunkers. From there it is sent along a conveyor either to a ball mill (for grinding) or to turbo solvents (for dissolving clay and kaolin)

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• Pottery has been known since time immemorial. Clay was a ubiquitous material at hand, the rich plastic and artistic possibilities of which attracted people even in ancient times. Clay is very easy to process; you can sculpt anything from it.

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• Depending on the structure, a distinction is made between fine ceramics (vitreous or fine-grained shards) and coarse ceramics (coarse-grained shards). The main types of fine ceramics are porcelain, semi-porcelain, faience, majolica. The main type of coarse ceramics is pottery ceramics.

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• Porcelain vase from the collection of Chinese porcelain from the Qing Dynasty (XVII-XIX centuries) in the Kunstkamera (St. Petersburg).

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Egyptian goddess Tawaret from faience

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majolica

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pottery ceramics

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• CERAMIC URN - an example of Mayan pottery art.
• Working on a potter's wheel. Image on ceramic tiles.

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• Cement is widely used in construction - one of the types of ceramics, the raw materials for which are clay and limestone mixed with water.

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History of domestic ceramic tiles

• In Rus', ceramic tiles appeared in the 9th century with the advent of Christianity. During the pagan period, stone and wood were predominantly used as building materials.

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General information

Ceramic products are products obtained from mineral raw materials by molding and firing at high temperatures. The term “ceramics” comes (according to P.P. Budnikov) from the word “ceramia”, which in Ancient Greece was used to describe the art of making clay products. And now in ceramic technology they mainly use clays, but along with them they also use other types of mineral raw materials, for example pure oxides (oxide technical ceramics). Ceramic materials are the most ancient of all artificial stone materials. Shards of crude pottery are found at the site of settlements dating back to the Stone Age. The age of ceramic brick as a building material is more than 5000 years. Ancient ceramic roofing Ceramic panels Red-figure wall ceramics

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In modern construction

Ceramic products are used: in almost all structural elements of buildings in prefabricated and individual housing construction (cladding materials) in the decoration of building facades and interiors; ceramic porous aggregates are the basis of lightweight concrete; sanitary products, dishes made of porcelain and earthenware; special ceramics for the chemical and metallurgical industries. industry (acid-resistant and fire-resistant products), electrical engineering and radio electronics (electrical insulators, semiconductors, etc.), space technology

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CLASSIFICATION

By purpose: - wall products (brick, hollow stones and panels made from them); - roofing products (tiles); - floor elements; - products for cladding facades (facing bricks, small-sized and other tiles, typesetting panels, architectural and artistic details); - products for internal wall cladding (glazed tiles and shaped parts for them - cornices, corners, corbels); - fillers for lightweight concrete (expanded clay, agloporite); - thermal insulation products (perlite ceramics, cellular ceramics, diatomaceous earth, etc.); - sanitary products (wash tables, bathtubs, toilets); - floor tiles; - road brick; - acid-resistant products (bricks, tiles, pipes and fittings for them); - refractories; - products for underground communications (sewage and drainage pipes).

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Depending on the structure: porous, dense (sintered shard). Porous ones absorb more than 5% of water (by mass), on average their water absorption is 8-20% by mass or 14-36% by volume. These include products of both coarse ceramics - ceramic wall bricks and stones, products for roofing and ceilings, drainage pipes, and fine ceramics - facing tiles, earthenware. Dense absorb less than 5% of water, more often 1-4% by mass or 2-8% by volume. These also include products made from coarse ceramics - clinker bricks, large-sized facing slabs, and fine ceramics - earthenware, semi-porcelain, porcelain.

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By melting point: low-melting - with a melting point below 1350 °C; refractory - with a melting point of 1350°C-1580°C; fireproof - 1580 -2000 °C; highest fire resistance - more than 2000 °C.

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Raw materials

KAOLIN – consist of the mineral Al2O3 2SiO2 2H2O, contain a significant amount of particles less than 0.01 mm, after firing they retain a white color; CLAYS – varied in mineral composition, more contaminated with mineral and organic impurities; clayey matter (with particles less than 0.005 mm) consists mainly of kaolinite and related minerals - montmorillonite Al2O3 4SiO2 nH2O, halloysite Al2O3 2SiO2 4H2O; the content of fine particles determines the plasticity and other properties of clays; may contain impurities that reduce the melting point (calcium carbonate, feldspar, Fe(OH)3, Fe2O3); stone-like inclusions of CaCO3 are the cause of the appearance of “bullet” cracks in ceramic products, because hydration of the CaO obtained during firing is accompanied by an increase in its volume; the color of clay depends on impurities of mineral and organic origin (from white, brown, green, gray to black), the usual red color of clay is given by an admixture of iron oxide; bentonites – highly dispersed clayey rocks with a predominant content of montmorillonite; tripoli and diatomites - consist mainly of amorphous silica; used for the manufacture of thermal insulation products, building bricks and stones.

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Thinning materials - to reduce plasticity and reduce air and fire shrinkage of clays: fireclay with grains of 0.14-2 mm (refractory clay, kaolin) - improves the drying and firing properties of clays, used to produce high-quality products - facing bricks, refractories, etc. dehydrated clay - improves the drying properties of raw materials and the appearance of bricks sand with grains of 0.5-2 mm granulated blast furnace slag with grains up to 2 mm - an effective clay thickener in the production of bricks thermal power plant ash burn-out additives Pore-forming materials - for producing light ceramic products with increased porosity and reduced thermal conductivity. They use substances that, during firing, dissociate with the release of gas (ground chalk, dolomite) or burn out (burn-out additives: sawdust, crushed brown coal, waste from coal preparation plants, thermal power plant ash and lignin, they increase the porosity of products and promote uniform sintering of ceramic shards)

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Plasticizing additives - highly plastic clays, bentonites, surfactants (sulphite-yeast mash) Fluins - reducing the sintering temperature of clay (feldspars, iron ore, dolomite, magnesite, talc, etc.) Glaze or engobe - imparting a decorative appearance and resistance to external influences. A layer of glaze (transparent and/or opaque (solid) glass of various colors) is applied to the surface of the ceramic material and fixed to it by firing at high temperature. The main raw materials of the glaze (quartz sand, kaolin, feldspar, salts of alkali alkaline earth metals, lead or strontium oxides, boric acid, borax, etc.) are used in raw form or fused - in the form of a frit. Engobe is prepared from white or colored clay and applied in a thin layer to the surface of an unfired product. Engobe does not melt when fired, so the surface is matte. Its properties should be close to the main shard.

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PRODUCTION OF CERAMIC MATERIALS

Molding methods - plastic and semi-dry With the plastic method, the humidity of the molding mixture is 15-25%, which requires mandatory drying of the molded products before firing. With the semi-dry method, drying is not required, since the moisture content of the clay is 6-7%, and the products are molded on special presses under significant pressure of 15-40 MPa. Such bricks have the correct shape and exact dimensions, but are less frost-resistant. Burnout - products lose their shape and melt from the surface; Underburning (incompleteness of the sintering process (“scarlet” color of the brick) - reduced strength, a strong decrease in water resistance and frost resistance

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Properties of clays as raw materials for ceramic products

Clay mixed with a certain amount of water forms a clay dough that has cohesion and plasticity. When dry clay is wetted, the characteristic smell of moistened earth and the release of heat are felt. Water molecules (dipoles) are drawn between the scaly kaolinite particles and wedge them, causing the clay to swell. Thin layers of water between lamellar particles of clay minerals give rise to the characteristic properties of clay dough. The plasticity of clays is explained by the fact that when moistened, thin films of adsorbed water appear on the surface of the particles, which ensure the sliding of the particles and bind them through the forces of intermolecular interaction. Plasticity is assessed by the amount of water required to obtain a moldable mass. Clays can be highly plastic, medium plastic and low plastic. The more clay minerals there are in clay, the more water it requires, the more it swells, the more difficult it is to dry and the more it shrinks. Such clays are called fatty. Clays containing a lot of sand particles are called lean. Optimal mixtures are obtained by introducing lean additives into fatty clays - sands, thermal power plant ash, slag, fireclay, etc.

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The binding ability of clay is manifested in the binding of grains of non-plastic materials (sand, fireclay, etc.), as well as in the formation of a fairly durable product upon drying - raw material. The peculiarity of clay dough is its ability to harden when dried in air. Capillary pressure forces pull clay particles together and prevent their separation, resulting in air shrinkage. Shrinkage is a decrease in the linear dimensions and volume of raw clay during drying (air shrinkage) and firing (fire shrinkage) of clay (and together - complete shrinkage); expressed as a percentage of the original size of the product. Caking ability is the ability of clays to transform into a stone-like state when fired (900-1200 oC). The formation of a durable shard occurs due to the effect of gluing together solid clay particles with the resulting melt.

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Properties of ceramic products

The porosity of a ceramic shard (porous products) increases by 10-40% with the introduction of pore-forming additives into the ceramic mass. In an effort to reduce density and thermal conductivity, they resort to creating voids in bricks and ceramic stones. Water absorption characterizes the porosity of a ceramic shard. Porous ceramic water absorption is 6-20% by weight, i.e. 12-40% by volume of dense products water absorption - 1-5% by mass and 2-10% by volume

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The thermal conductivity of an absolutely dense ceramic shard is high - 1.16 W/(m·ᵒС). Air pores and voids created in ceramic products reduce density and significantly reduce thermal conductivity. For example, for wall ceramic products from 1800 to 700 kg/m3 and from 0.8 to 0.21 W/(m·ᵒС), respectively. As a result, the thickness of the outer wall and the material consumption of the enclosing structures are reduced. Strength depends on the phase composition of the ceramic shard, porosity and the presence of cracks. The grade of a wall ceramic product (brick, etc.) in terms of strength indicates the compressive strength, however, when establishing the grade of a brick, along with the compressive strength, the bending strength is taken into account, since the brick in the masonry is subject to bending. Products with porous shards are produced in the M75-M300 grades, and dense products (road bricks, etc.) - M400-M1000.

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Frost resistance. The frost resistance grade denotes the number of cycles of alternating freezing and thawing that a ceramic product can withstand in a water-saturated state without signs of visible damage (delamination, peeling, cracking, chipping). Depending on their structure, products have the following brands: F15, F25, F35, F50, F75, F100. The vapor permeability of wall ceramic products contributes to room ventilation, depending on the porosity and nature of the pores. Low vapor permeability is the reason for sweating on the inner surface of the walls of rooms with high air humidity. Uneven vapor permeability of the layers that make up the outer wall - accumulation of moisture. Thus, facade cladding of walls with glazed tiles can lead to the accumulation of moisture in the wall-tile contact layer, and subsequent freezing of the moisture causes peeling of the cladding.

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Application

Structural products operated under load conditions include wall materials (bricks and ceramic stones), roofing materials (tiles), water, sewer and drainage pipes. In addition, brick is used for laying columnar foundations in low-rise buildings, as well as for the factory production of large-sized blocks and panels, which, depending on the purpose (for internal or external walls), can be one-, two-, or three-layer. In multilayer ones, slab insulation is used to increase heat-shielding properties.

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Special purpose materials include: sanitary, acid-resistant, fire-resistant, heat-insulating. Application The main raw materials for the production of sanitary products are white-burning clays mixed with glass-forming fluxes and waste additives. By changing the ratio of components and the technology of molding and firing, earthenware, semi-porcelain and porcelain products are obtained, which are respectively listed in increasing order of their density and strength. The largest volume in construction falls on relatively porous earthenware products, the water resistance of which is ensured by glazing the surface.

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Acid-resistant materials in the form of tiles and bricks of classes A, B, C, obtained from acid-resistant clays, are used to protect floors, walls, and technological equipment at chemical plants. The main purpose of refractory materials is the lining of high-temperature technological equipment. The maximum operating temperature of such products is determined by the composition of the raw material: with an increased content of silica (Si02) silica refractories are obtained (up to 1650 °C), fireclay - fireclay (up to 1400 °C), alumina (A1203) - high-alumina (over 1750 °C). Application

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Thermal insulation materials and products based on clay raw materials are produced in the form of highly porous diatomite foam bricks, used mainly for thermal insulation of technological equipment, and loose bulk materials: expanded clay gravel and agloporite crushed stone. The latter are obtained by swelling of molded granules at temperatures above 1000°C or by crushing sintered raw materials with coal waste and are used as thermal insulation backfill for insulating floors, ceilings, walls, as well as lightweight concrete aggregates for various purposes. Application

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Wall and roofing ceramic materials

Modern brick sizes were legalized by the standard in 1927. In accordance with it, bricks are produced in sizes 250x120x65 and 250x120x88. The weight of one brick should not exceed 4.3 kg. Therefore, thickened bricks are usually produced with voids. The following names of brick faces are accepted: bed, spoon, poke. 1-bed, 2-spoon, 3-poke

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Physical properties of ordinary solid ceramic bricks: average density should not exceed 1600-1800 kg/m3, porosity - 28-35%, water absorption - not less than 8%. The main characteristic of brick quality is the grade of compressive and bending strength. 8 grades have been established from 75 to 300. In terms of frost resistance for brick, four grades have been established F15, F25, F35, F50. The standard allows large deviations in the size and shape of bricks due to large uneven shrinkage during its manufacture.

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Due to its fairly high physical and mechanical characteristics, ordinary ceramic brick is widely used in modern construction for laying walls, foundations, chimneys and other structures. Semi-dry pressed bricks cannot be used for foundations and walls of wet rooms. More industrial in manufacturing technology and thermal characteristics are hollow ceramic bricks and blocks with dimensions: 250x120x138, 380x120x138, 250x250x138. Stones are considered hollow if their void volume is more than 13%. The shape and size of voids may vary. The location of the voids is predominantly vertical. Hollow stones cannot be used for laying structures in contact with water. Freezing of water trapped in voids. may destroy the stone. The presence of voids not only reduces the weight of products, but also speeds up and facilitates the drying and firing processes. They have much fewer defects, and their strength is the same as that of solid brick. Ordinary solid brick Ordinary hollow brick Hollow brick blocks

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Natural ceramic or clay tiles are one of the oldest roofing materials. The history of its use goes back more than one millennium. Ceramic tiles are the most popular material in Europe: more than half of European pitched roofs are ceramic. Such popularity of tiles is due, first of all, to their unique characteristics: Attractive appearance; Durability; Fire resistance; Environmental friendliness; Resistance to aggressive environments, ultraviolet radiation and wind loads; Low thermal conductivity, ability to absorb noise. The raw materials for tiles are brick clays with improved preparation quality. The disadvantage of tiled roofing is its large mass and labor-intensive installation.

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ANGOB NATURE GLAZE

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Finishing ceramic materials

There are finishing ceramics for external, internal cladding and floor coverings. Facing brick has an improved surface quality; it is made from white and red-burning clays. Sometimes it is given color with coloring additives. It is decorated with engobes and two-layer molding to save white-burning clays. Glazes are sometimes used; they are decorative and very durable (retain their color for hundreds of years). Facing brick Carpet and mosaic coverings

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Ceramic tiles in the form of a carpet are embedded in the mortar or concrete of the walls, followed by washing off the paper base. This process can be carried out both at the factory and at the construction site. Facade ceramic tiles are used for external cladding of buildings and underground structures. They are produced in various sizes from 65x120 to 600x1200 mm. The back side of the tiles is corrugated. Large-sized ones are mounted on facades using metal fixtures. One of the options for such slabs is called ceramic granite. Terracotta is a classic ancient and modern material obtained by firing clay and subsequent surface treatments. Large-sized facing products in the form of slabs, parts of columns, platbands and other architectural details were used back in Ancient Greece. It was revived during the construction of all high-rise buildings in Moscow in the 40-50s. Shaped terracotta products for facades Terracotta plates for design projects Handmade terracotta tiles Carpet terracotta mosaic

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Tiles for interior wall cladding are produced in a variety of sizes from 70x70 to 330x330. They also produce various additional elements for it - friezes, belts, etc. The tiles have a porous shard and are covered with glaze on the front side, which not only decorates them, but also gives them water and chemical resistance. These tiles are used in damp areas. They cannot be used for flooring or exterior finishing. Floor tiles are made from refractory clays. They have almost no pores and are practically waterproof. They are often called Mettlach (from the name of the German city Mettlach). Tiles can be painted throughout or have a painted top layer. They have high wear resistance and strength. This floor is called cold due to the high heat absorption of the ceramic coating. In Russia, it is customary to install floors made from such tiles in rooms with damp operating conditions.

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CERAMIC GRANITE This material is relatively new, but has already gained popularity among those who like to build and rebuild. Porcelain tiles (gres) are unenamelled, single-fired ceramic tiles made from light clays, quartz sand, feldspar and mineral pigment dyes. Porcelain tiles with a base of red clay are called “red gres”. Advantages: low water absorption coefficient - less than 0.05% (for comparison: for natural granite - 0.5%) resistance to temperature changes, hardness, non-porous structure, impact resistance, abrasion resistance. Wood-look porcelain tiles

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Ceramic tiles for wall decoration

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Photoceramics

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Ceramic plinth for floors A standard ceramic plinth has a triangular shape at the base with a concave middle or relief. But flat friezes with a narrow base and a soft chamfer along the upper edge are no less popular. The use of such skirting boards facilitates the process of installing furniture, since it can be moved almost flush against the wall. The height of the products is also different - from narrow 1.5 cm to wide 8-10 cm, however, taking into account the height of the tiles in a particular collection. The surface can be plain, patterned or textured, with either a matte or glossy finish. The plinth is selected not only to finish the joint between the floor and the wall, but also to close the gap between the wall and the bathtub (sink), since traditionally in our country plumbing equipment is placed close to the wall to save space. Skirting boards, pencils, friezes, belts and borders

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Special types of ceramic materials

Sanitary ceramics (sinks, toilets, pipes) are made from earthenware and porcelain. Faience is a thin ceramics made from white-burning clays (60...65%), quartz (30...35%) and feldspar (3...5%). The molded and dried product is fired twice: first, and after applying the glaze again. Glazing of faience is necessary, since it has a porous shard (P = 20...25%) and high water absorption.

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Porcelain – fine ceramic products. It is obtained in the same way as earthenware, slightly changing the composition of the raw materials (up to 20...25% feldspar content). Porcelain has a dense, fully sintered shard that is translucent in a thin layer. Porcelain products for sanitary purposes are also glazed to give them smoothness and improve sanitary and hygienic properties. Ceramic sanitary products are distinguished by their decorative properties and universal chemical resistance; Thanks to their hard and smooth surface, they are easy to clean and retain their properties for a long time. The disadvantage of such products, as well as ceramics in general, is fragility. But despite this, ceramics remains the best material for sanitary products. Sewer pipes are made from plastic, refractory clays and glazed on the outside and inside, which ensures their complete waterproofness, chemical resistance and high throughput. They are designed for a pressure of 0.2 MPa. Their length is 800-1200 mm, diameter 150-600 mm.

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Refractory ceramic materials

Refractory materials are produced using ceramic technology from various raw materials. They are divided into fire-resistant (softening temperature 1580...1770 o C), highly fire-resistant (1770...2000 o C) and highest fire resistance (>2000 o C). Depending on the chemical and mineralogical composition, refractories can be siliceous, aluminosilicate, magnesium, chromite, or graphite. Siliceous refractories (the main component is (SiO 2)) in structure can be glassy (quartz glass) and crystalline (silica refractories). Dinas refractories are produced by firing quartz raw materials (ground quartz sand with the addition of lime or other binders) at a temperature of about 900 o C. The refractoriness of these materials - 1600...1700o C. They are used for constructing the roofs of glass melting and glass melting furnaces.

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Quartz glass works well at temperatures up to 1000 o C; at higher temperatures it devitrifies (crystallizes) and crumbles. Aluminosilicate refractories are divided into three groups: semi-acid and fireclay and high-alumina. Semi-acid refractories are made by firing quartz rocks on a clay binder. The fire resistance of these materials is 1580...1700 oC. Fireclay refractories are produced by firing a mixture of fireclay and refractory clay. They are characterized by heat resistance and slag resistance. Their fire resistance is up to 1500 °C. High alumina refractories contain more than 45% alumina. They are obtained from bauxite. When the alumina content increases to 60%, the fire resistance of these materials can reach 2000 °C. They are used for laying blast furnaces and glass furnaces.

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