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Ceramic Materials

I. History
II. Classification of Ceramics based on its application and composition
III. Processing of Ceramics

Published in: Technology
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  1. 1. CERAMICS ES311: Engineering Materials
  2. 2. What are Ceramic Materials?  Inorganic, nonmetallic materials that consist of metallic and nonmetallic elements bonded together primarily by ionic and/ or covalent bonds  Its chemical compositions vary considerably, from simple compounds to mixtures of many complex phases bonded together.  Ceramics used for engineering applications, can be divided into two groups: 1) Traditional ceramic materials 2) Advanced ceramic materials  Typically hard and brittle with low toughness and ductility  Usually good electrical and thermal insulators  Normally have relatively high melting temperatures and high chemical stability in many hostile environments
  3. 3. History of Ceramics
  4. 4. Ceramic Crystal Structure  Broader range on chemical composition than metals with more complicated structures  contains at least 2 and often 3 or more atoms  usually compounds between metallic ions (e.g. Fe, NI, Al) -called cations - and non- metallic ions (e.g. O, N, Cl) -called anions  Bonding will usually have some covalent character but is usually mostly ionic
  5. 5. Example Ceramic Crystal Structure
  6. 6. *Classification of Ceramics based on APPLICATION
  7. 7. Traditional Ceramics  Made from three basic components: clay, silica (flint), and feldspar. o The clay in traditional ceramics provides workability of the material before firing hardens it and constitutes the major body material. o The silica has a high melting temperature and is the refractory component of traditional ceramics. o Potash feldspar, has a low melting temperature and makes a glass when the ceramic mix is fired. It bonds the refractory components together.  A type of ceramic used in traditional applications such as construction, earthenware, and glassware.
  8. 8. Whitewares Made from components of clay, silica, and feldspar for which the composition is controlled. Example: ◦ Electrical porcelain ◦ Dinner china ◦ Sanitary ware
  9. 9. Whitewares Electrical porcelain
  10. 10. Whitewares Dinner China
  11. 11. Whitewares Sanitary ware
  12. 12. Structural Clay Products Made of natural clay, which contains all three basic components. Example: ◦ Building brick ◦ Sewer pipe ◦ Drain tile ◦ Roofing tile ◦ Floor tile
  13. 13. Structural Clay Products Building brick
  14. 14. Structural Clay Products Sewer pipe
  15. 15. Structural Clay Products Drain tile
  16. 16. Structural Clay Products Roofing tile
  17. 17. Structural Clay Products Floor tile
  18. 18. Brick and Tile  structural clay products, manufactured as standard units, used in building construction  is a small building unit in the form of a rectangular block, formed from clay or shale or mixtures and burned (fired) in a kiln, or oven, to produce strength, hardness, and heat resistance
  19. 19. Brick and Tile
  20. 20. Abrasives  is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away  a material often means polishing it to gain a smooth, reflective surface which can also involve roughening as in satin, matte or beaded finishes
  21. 21. Abrasives
  22. 22. Refractories  is one that retains its strength at high temperature Example: okiln linings ogas fire radiants osteel oglass making crucibles
  23. 23. Refractories KILN LININGS
  24. 24. Refractories Gas fire radiants
  25. 25. Refractories STEEL
  26. 26. Refractories glass making crucibles
  27. 27. Cements  is a binder, a substance that sets and hardens independently, and can bind other materials together  used in construction can be characterized as being either hydraulic or non-hydraulic  The most important uses of cement are as an ingredient in the production of mortar in masonry, and of concrete, a combination of cement and an aggregate to form a strong building material
  28. 28. Cements
  29. 29. Advanced Ceramics  Advanced ceramics are ideally suited for industrial applications that provide a physical interface between different components due to their ability to withstand high temperatures, vibration and mechanical shock.  A type of ceramic exhibiting a high degree of industrial efficiency.  A type of ceramic used in specialized, recently developed applications.  Advanced ceramics often have simple chemical compositions, but they are difficult to manufacture.
  30. 30. Electroceramics  is a class of ceramic materials used primarily for their electrical properties. Further classified to: Dielectric ceramics Fast ion conductor ceramics Piezoelectric and ferroelectric ceramics
  31. 31.  Dielectric Ceramics  are capable of storing large amounts of electrical charge in relatively small volumes.  Is an electrical insulator that can be polarized by an applied electric field.  Dielectric materials can be solids, liquids, or gases.  Solid dielectrics are perhaps the most commonly used dielectrics in electrical engineering, and many solids are very good insulators.
  32. 32. sulfur hexafluoride (SF6) Solid Dielectric Liquid Dielectric Gas Dielectric
  33. 33.  are solids in which ions are highly mobile. These materials are important in the area of solid-state ionics, and are also known as solid electrolytes and superionic conductors.  These materials are useful in batteries and various sensors. Fast ion conductors are used primarily in solid oxide fuel cells.  Fast Ion Conductor Ceramics
  34. 34.  Piezoelectric Ceramics ◦ Piezoelectric ceramic materials are categorized as functional ceramics. ◦ In sensors they make it possible to convert forces, pressures and accelerations into electrical signals, and in sonic and ultrasonic transducers and actuators they convert electric voltages into vibrations or deformations. ◦ Piezo-ceramics have a wide range of uses. Piezo-ceramics are used in the automotive industry in a number of applications such as in knock and oil level sensors or as actuators for precise control of injection processes in engines. ◦ In medical technology piezo-ceramic components can be found in lithotripters, devices for plaque removal and in inhalers. Common applications in mechanical engineering include ultrasonic cleaning, ultrasonic welding and active vibration damping.
  35. 35.  Magnetic Ceramics  Magnetic ceramics are made of ferrites, which are crystalline minerals composed of iron oxide in combination with some other metal. They are given the general chemical formula M(FexOy), M representing other metallic elements than iron. The most familiar ferrite is magnetite, a naturally occurring ferrous ferrite (Fe[Fe2O4], or Fe3O4) commonly known as lodestone. The magnetic properties of magnetite have been exploited in compasses since ancient times. Magnetic bracelet Ceramic Magnets
  36. 36.  Magnetic Ceramics  Soft Ferrites o Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. They have a low coercivity and are called soft ferrites. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. Because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power supplies.
  37. 37.  Magnetic Ceramics  Hard Ferrites o In contrast, permanent ferrite magnets are made of hard ferrites, which have a high coercivity and high remanence after magnetization. Iron oxide and barium or strontium carbonate are used in manufacturing of hard ferrite magnets. The high coercivity means the materials are very resistant to becoming demagnetized, an essential characteristic for a permanent magnet. They also conduct magnetic flux well and have a high magnetic permeability. This enables these so-called ceramic magnets to store stronger magnetic fields than iron itself. They are cheap, and are widely used in household products such as refrigerator magnets.
  38. 38.  Optical Ceramics  are polycrystalline materials produced through controlled crystallization of base glass.  Glass-ceramic materials share many properties with both glasses and ceramics.  Glass-ceramics have an amorphous phase and one or more crystalline phases and are produced by a so-called "controlled crystallization" in contrast to a spontaneous crystallization, which is usually not wanted in glass manufacturing.  Glass-ceramics have the fabrication advantage of glass as well as special properties of ceramics.  Glass ceramics has a variety of properties such as, high strength, toughness, translucency or opacity, opalescence, low or even negative thermal expansion, high temperature stability.
  39. 39.  Optical Ceramics Watch Glasses High-pressure sodium-vapour lamp bulb Optical Glass Lenses
  40. 40. Advance Structural Ceramics  ceramic materials that demonstrate enhanced mechanical properties under demanding conditions. Because they serve as structural members, often being subjected to mechanical loading, they are given the name structural ceramics. Ordinarily, for structural applications ceramics tend to be expensive replacements for other materials, such as metals, polymers, and composites.
  41. 41. Advance Structural Ceramics Classified to: o Nuclear Ceramics o Bioceramics o Tribological Ceramics o Automotive Ceramics
  42. 42.  Nuclear Ceramics  nuclear ceramics, ceramic materials employed in the generation of nuclear power and in the disposal of radioactive nuclear wastes.  In their nuclear-related functions, ceramics are of major importance. Since the beginning of nuclear power generation, oxide ceramics, based on the fissionable metals uranium and plutonium, have been made into highly reliable fuel pellets for both water-cooled and liquid-metal-cooled reactors. Ceramics also can be employed to immobilize and store nuclear wastes. Although vitrification (glass formation) is a favoured approach for waste disposal, wastes can be processed with other ceramics into a synthetic rock, or synroc, or they can be mixed with cement powder to make hardened cements. All these nuclear applications are extremely demanding. In addition to severe thermal and chemical driving forces, nuclear ceramics are continuously subjected to high radiation doses.
  43. 43.  Nuclear Ceramics The image above shows a vintification process or encapsulating nuclear waste in glass is a possible method of containing nuclear wastes
  44. 44.  Bioceramics  ceramic products or components employed in medical and dental applications, mainly as implants and replacements.  Bioceramics range in biocompatibility from the ceramic oxides, which are inert in the body, to the other extreme of resorbable materials, which are eventually replaced by the materials which they were used to repair.  Bioceramic materials are commonly subdivided by their bioactivity. Bioinert materials, (such as Oxide ceramics, Silica ceramics, Carbon fiber) are non-toxic and non- inflammatory. These materials must be long lasting, structural failure resistant, and corrosion resistant. Bioceramics additionally must have a low Young's modulus to help prevent cracking of the material.
  45. 45.  Bioceramics  Ceramics are now commonly used in the medical fields as dental, and bone implants. Artificial teeth, and bones are relatively commonplace. Surgical cermets are used regularly. Joint replacements are commonly coated with bioceramic materials to reduce wear and inflammatory response. Other examples of medical uses for bioceramics are in pacemakers, kidney dialysis machines, and respirators. Hip Prosthesis Femoral Head of a Hip Prosthesis
  46. 46.  Tribological Ceramics  Tribological ceramics, also called wear-resistant ceramics, ceramic materials that are resistant to friction and wear. They are employed in a variety of industrial and domestic applications, including mineral processing and metallurgy.  Advanced structural ceramics offer unique capabilities as tribomaterials.  They are being used today in diverse applications such as tips for ball-point pens, precision instrument bearings, and cutting tool inserts.  Tribological applications of ceramics can be divided into several categories based on the properties of the ceramics. These include: resistance to abrasion and erosion; resistance to corrosive wear; wear resistance at elevated temperatures; low density; and electrical, thermal and magnetic properties.
  47. 47.  Tribological Ceramics Tip of a ball Point Pen Ceramic Instrumental Bearing
  48. 48.  Automotive Ceramics  Automotive ceramics, advanced ceramic materials that are made into components for automobiles. Examples include spark plug insulators, catalysts and catalyst supports for emission control devices, and sensors of various kinds. Its powerful physical, thermal and electrical properties make it a reliable, highly durable and cost- effective alternative to metal. As the industry faces continued pressure to deliver innovative design, improved safety features and environment-friendly vehicles (while also reducing production costs), use of this material looks set to grow. Spark Plug Insulators Catalytic Converter
  49. 49. *Classification of Advanced Ceramics based on COMPOSITION  NITRIDE CERAMICS  Nitrides used in ceramics consist of nitrogen atoms bonded to elements such as silicon and aluminum.
  50. 50. Silicon Nitride  is a chemical compound of the elements silicon and nitrogen, with the formula Si3N4. It is a white, high-melting-point solid that is relatively chemically inert, being attacked by dilute HF and hot H2SO4. It is the most thermodynamically stable of the silicon nitrides. Hence, Si3N is the most commercially important of the silicon nitrides and is generally understood as what is being referred to where the term "silicon nitride" is used.
  51. 51. Silicon Nitride Applications: o Wear Guides o Seals and Bearings o Grinding Media
  52. 52. Aluminum Nitride  a covalently bonded ceramic is synthesized from abundantly available elements Al and N. The ceramic does not occur naturally. AlN has a Wurtzite crystal structure and is stable in inert atmospheres at temperatures in excess of 2000°C. It exhibits high thermal conductivity property while remaining a strong dielectric. This unusual combination of properties is what makes Al N a critical advanced materials for many future applications in Optics, lighting, electronics and green environmental technologies.s an intermetallic inorganic compound with the chemical formula Pb[ZrxTi1-x]O3 0≤x≤1). Also called PZT, it is a ceramic perovskite material that shows a marked piezoelectric effect, which finds practical applications in the area of electroceramics. It is a white solid that is insoluble in all solvents.
  53. 53. Aluminum Nitride  opto-electronics  dielectric layers in optical storage media  electronic substrates, chip carriers where high thermal conductivity is essential  military applications APPLICATION
  54. 54. Silicon Aluminum Oxynitride  are a specialist class of high-temperature refractory materials, with high strength (including at high temperature), good thermal shock resistance and exceptional resistance to wetting or corrosion by molten non-ferrous metals, compared to other refractory materials such as, for example, alumina. A typical use is with handling of molten aluminium. They also are exceptionally corrosion resistant and hence are also used in the chemical industry. Sialons also have high wear resistance, low thermal expansion and good oxidation resistance up to above ~1000 °C.
  55. 55. Silicon Aluminum Oxynitride APPLICATION oThermocouple protection tubes for nonferrous metal melting oImmersion heater and burner tubes oDegassing and injector tubes in nonferrous metals. Metal feed tubes in aluminum die casting oWelding and brazing fixtures and pins
  56. 56. *Classification of Advanced Ceramics based on COMPOSITION  SILICATE CERAMICS  Silicates are materials composed generally of silicon and oxygen. Silicate ceramic components are used in electronics and electrical engineering and act as electrical insulation in fuses, circuit breakers, thermostats and in lighting technology. The ability of silicate ceramic materials to provide thermal insulation is also utilized in heating, environmental and thermal engineering applications.
  57. 57. Porcelain - is a ceramic material made by heating materials, generally including clay in the form of kaolin, in a kiln to temperatures between 1,200 °C (2,192 °F) and 1,400 °C (2,552 °F). The toughness, strength, and translucence of porcelain arise mainly from the formation of glass and the mineral mullite within the fired body at these high temperatures. Porcelain Vase Porcelain Tile
  58. 58. Magnesium Silicate • is a chemical compound consisting of magnesium, silicon, and oxygen. It exists in several forms, both natural and manufactured. One of the most common forms of this compound is the mineral talc, which can be found in deposits around the world and is used in many industrial and everyday applications. Synthetic forms are also widely used, especially as filters and additives in the food industry. • The material is lower in cost than Alumina but offers reduced mechanical properties. However it has very good electrical resistance properties, which are retained at high temperatures, along with moderate mechanical strength and temperature resistance. It has been used in electrical insulation for many years in both large-scale electrical systems and electronic and domestic appliances.
  59. 59. Magnesium Silicate Applications: Bases for halogen lamps Switches and Plug Parts
  60. 60. Mullite • Mullite is the mineralogical name given to the only chemically stable intermediate phase in the SiO2 - Al2O3 system. • Mullite is commonly denoted as 3Al2O3 .2SiO2 (i.e. 60 mol% Al2O3). However it is actually a solid solution with the equilibrium composition limits of 60 – 63mol % Al2O3 below 1600o C. • By far the largest use of mullite based products is in refractories. The glass and steel industries are two main markets. • The good mechanical properties at high temperatures of high purity mullites have made them potential high temperature engineering ceramics, for example in turbine engine components. • Other applications include electronic substrates and protective coatings.
  61. 61. Mullite Uniform 1micron thick protective mullite coating on a 15 micron . diameter SiC fiber A selection of mullite-based refractory shapes for the steel industry
  62. 62. *Classification of Advanced Ceramics based on COMPOSITION  CARBIDE CERAMICS  Carbide ceramics are extremely resistant against high temperature, abrasion and corrosion. They have a high thermal and variable electrical conductivity, and are mainly used in mechanical engineering, chemical, and power engineering, microelectronics as well as space engineering.
  63. 63. Boron Carbide (B4C)  crystalline compound of boron and carbon. It is an extremely hard, synthetically produced material that is used in abrasive and wear-resistant products, in lightweight composite materials, and in control rods for nuclear power generation.  With a Mohs hardness between 9 and 10, boron carbide is one of the hardest synthetic substances known, being exceeded only by cubic boron nitride and diamond.
  64. 64. Boron Carbide (B4C) o Padlocks o Abrasives o Cutting Tools o Grit Blasting nozzles APPLICATION
  65. 65. Silicon Carbide (SiC)  exceedingly hard, synthetically produced crystalline compound of silicon and carbon.  Its chemical formula is SiC.  an important material for sandpapers, grinding wheels, and cutting tools.  More recently, it has found application in refractory linings and heating elements for industrial furnaces, in wear- resistant parts for pumps and rocket engines, and in semiconducting substrates for light-emitting diodes.
  66. 66. Silicon Carbide (SiC) APPLICATIONS: o Abrasives or Cutting Tools (e.g. Grinding Wheel, Sandpaper) o Burner Nozzle o Spray Nozzle o Automobile Parts (e.g. Disc Brakes)
  67. 67. Tungsten Carbide  is an inorganic chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms.  In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery, cutting tools, abrasives, armor-piercing rounds, other tools and instruments, and jewelry.
  68. 68. Tungsten Carbide APPLICATION o Drill Bits o Surgical Imstruments o Jewelry
  69. 69. *Classification of Advanced Ceramics based on COMPOSITION  OXIDE CERAMICS  An oxide is a chemical compound made up of oxygen combined with at least one other element. Most of the Earth’s crust consists of oxides.
  70. 70. Aluminum Oxide (Al2O3) Aluminium oxide is a chemical compound of aluminium and oxygen with the chemical formula Al2O3. It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium(III) oxide. It is commonly called alumina, and may also be called aloxide, aloxite, or alundum depending on particular forms or applications. It is exceptionally hard, strong, sharp abrasive made from a process in which alumina gel is dried and crushed. Ceramic aluminum oxide has the ability to refracture at the sub-micron level.
  71. 71. Aluminum Oxide (Al2O3) APPLICATIONS ◦ Medical prostheses ◦ Ballistic armour ◦ Electrical insulators ◦ Grinding media ◦ Wear components
  72. 72. Magnesium Oxide (MgO)  is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium.  It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding.  According to evolutionary crystal structure prediction, MgO2 is thermodynamically stable at pressures above 116 GPa, and a totally new semiconducting suboxide Mg3O2 is thermodynamically stable above 500 GPa.  Magnesium oxide is produced by the calcination of magnesium carbonate or magnesium hydroxide or by the treatment of magnesium chloride with lime followed by heat.
  73. 73. Magnesium Oxide APPLICATIONS ◦ Heating elements ◦ Thermocouple tubes ◦ High temperature crucibles ◦ Cement
  74. 74. Zirconium Dioxide (ZrO2)  is one of the most studied ceramic materials. ZrO2 adopts a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at higher temperatures. The volume expansion caused by the cubic to tetragonal to monoclinic transformation induces large stresses, and these stresses cause ZrO2to crack upon cooling from high temperatures. When the zirconia is blended with some other oxides, the tetragonal and/or cubic phases are stabilized.
  75. 75. Zirconium Dioxide (ZrO2) APPLICATIONS ◦ Dental Ceramics ◦ Technical Cutters ◦ Tubes and Pipes ◦ Seal Rings, Bearings, Sealings
  76. 76. Aluminum Titanate (Al2TiO5)  a ceramic material consisting of a mixture of alumina (Al2O3) and titania (TiO2) forming solid solution with stoichiometric proportion of the components: Al2O3*TiO2 or Al2TiO5.  prepared by heating of a mixture of alumina and titania at temperature above 2460°F (1350°C).  The distinctive property of Aluminum Titanate ceramics is their high thermal shock resistance which is a result of very low coefficient of thermal expansion.  Disadvantage of Aluminum Titanate ceramics is relatively low mechanical strength caused by micro- cracks formed as a result of anisotropy of thermal expansion along the three primary axes of the crystal lattice (a single crystal of Aluminum Titanate expands along two axes and contract along the third axis when heated).
  77. 77. Aluminum Titanate (Al2TiO5) APPLICATIONS ◦ Riser Tubes ◦ Tubes and Pipes ◦ Thermocouples ◦ Dosing Tubes
  78. 78. Lead Zirconate Titanate  is an intermetallic inorganic compound with the chemical formula Pb[ZrxTi1-x]O3 0≤x≤1). Also called PZT, it is a ceramic perovskite material that shows a marked piezoelectric effect, which finds practical applications in the area of electroceramics. It is a white solid that is insoluble in all solvents.
  79. 79. Lead Zirconate Titanate APPLICATIONS ◦ Undersea exploration (sonar, beacons, imaging, current meters) ◦ Aerospace (gyroscopes, accelerometers, level sensing) ◦ Telecommunications (optical switching of telecom lines, buzzers and alarms, Haptics feedback, mobile phone cameras) ◦ Automotive (power seat controls, reversing/collision avoidance sensors, anti-knock sensors) ◦ Scientific research (nano positioning stages and analytical tools, scanning probe microscopy, advanced acoustics)
  80. 80. Amorphous Ceramics: Glasses  a ceramic material which is an inorganic product of fusion that has cooled to a rigid condition without crystallization  has a noncrystalline or amorphous structure The molecules in a glass change their orientation in a random manner throughout the solid material.
  81. 81. *Types of Glasses based on Composition  Fused silica glass, vitreous silica glass ◦ silica (SiO2). Has very low thermal expansion, is very hard and resists high temperatures (1000– 1500 °C). It is also the most resistant against weathering (alkali ions leaching out of the glass, while staining it). It is used for high temperature applications such as furnace tubes, melting crucibles, etc. ◦ the most important singe-component glass, has a high spectral transmission and is not subject to radiation damage, which cause browning of other glasses ◦ ideal glass for space vehicle windows, wind tunnel windows, and optical system in spectrophometric devices ◦ difficult to process and expensive
  82. 82. Fused silica glass, vitreous silica glass Space Vehicle Glass Windows Mirror SubstratesOptical Lenses Crucibles, trays and boats
  83. 83. *Types of Glasses based on Composition  Soda-lime-silica glass, window glass: ◦ silica 72% + sodium oxide (Na2O) 14.2% + magnesia (MgO) 2.5% + lime (CaO) 10.0% + alumina (Al2O3) 0.6%. Is transparent, easily formed and most suitable for window glass. It has a high thermal expansion and poor resistance to heat (500–600 °C). ◦ Used for flat glass, containers, pressed and blown ware, and lighting products where high chemical durability and heat resistant are not needed.
  84. 84. *Types of Glasses based on Composition  Sodium borosilicate glass, Pyrex ◦ silica 81% + boric oxide (B2O3) 12% + soda (Na2O) 4.5% + alumina (Al2O3) 2.0%. Stands heat expansion much better than window glass. Used for chemical glassware, cooking glass, car head lamps, etc. Borosilicate glasses (e.g. Pyrex) have as main constituents silica and boron oxide. ◦ They have fairly low coefficients of thermal expansion (7740 Pyrex CTE is 3.25×10–6/°C as compared to about 9×10−6/°C for a typical soda-lime glass), making them more dimensionally stable. The lower CTE also makes them less subject to stress caused by thermal expansion, thus less vulnerable to cracking from thermal shock. ◦ They are commonly used for reagent bottles, optical components and household cookware.
  85. 85. *Types of Glasses based on Composition  Lead-oxide glass, crystal glass ◦ silica 59% + soda (Na2O) 2.0% + lead oxide (PbO) 25% + potassium oxide (K2O) 12% + alumina 0.4% + zinc oxide (ZnO) 1.5%. Has a high refractive index, making the look of glassware more brilliant (crystal glass). It also has a high elasticity, making glassware 'ring'. It is also more workable in the factory, but cannot stand heating very well.
  86. 86. *Types of Glasses based on Composition  Aluminosilicate glass oA small, but important type of glass, aluminosilicate, contains 20% aluminium oxide (alumina-Al2O3) often including calcium oxide, magnesium oxide and boric oxide in relatively small amounts, but with only very small amounts of soda or potash. oIt is able to withstand high temperatures and thermal shock and is typically used in combustion tubes, gauge glasses for high- pressure steam boilers, and in halogen- tungsten lamps capable of operating at temperature as high as 750°C.
  87. 87. *Types of Glasses based on Composition Iphone’s Aluminosilicate Sheet Glass Boiler Gauge Glass Halogen-Tungsten Lamps
  88. 88. *Types of Glasses based on Composition • Oxide glass o alumina 90% + germanium oxide (GeO2) 10%. Extremely clear glass, used for fiber-optic wave guides in communication networks. Light loses only 5% of its intensity through 1 km of glass fiber. Fiber-Optic Waveguides
  89. 89. PROCESSING OF CERAMICS Most traditional and engineering ceramic products are manufacture by compacting powders or particles into shapes that are subsequently heated to a high enough temperature to bond the particles together.  The 3 basic steps in the processing of ceramics by the agglomeration of particles are: 1. Material Preparation 2. Forming and Casting 3. Thermal treatment by drying and firing
  90. 90. Material Preparation  Most ceramic products are made by the agglomeration of particles. The raw materials for these products vary, depending on the required properties of the finished ceramic part. The particles and other ingredients such as binders and lubricants may be blended wet and dry. For ceramic products that do not have very “critical” properties such as common bricks, sewer pipe, and other clay products, the blending of the ingredients with water is common practice. For some other ceramic products, the raw materials are ground dry along with binders and other additives. Sometimes wet and dry processing of raw materials are combined.
  91. 91. Forming  Pressing – ceramic particulate raw materials can be pressed in the dry, plastic, or wet condition into a die to form shaped products. 3 Types of Pressing: 1. Dry Pressing 2. Isostatic Pressing 3. Hot Pressing
  92. 92.  Dry Pressing - used commonly for products such as structural refractories (high- heat-resistant materials) and electronic ceramic components. - defined as the simultaneous uniaxial compaction and shaping of a granular powder along with small amounts of water and/ or organic binder in a die. - used extensively because it can form a variety of shapes rapidly with uniformity and close tolerance.
  93. 93.  Dry Pressing
  94. 94.  Isostatic Pressing– ceramic powder is loaded into a flexible (usually rubber), airtight container (called a bag) that is inside a chamber of hydraulic fluid to which pressure is applied. - after cold isostatic pressing, the part must be fired (sintered) to achieve the required properties and microstructure. - examples ceramic products manufactured are: refractories, bricks and shapes, spark plug insulators, radomes, carbide tools, crucibles, and bearings.
  95. 95.  Hot Pressing - ceramic parts of high density and improved mechanical properties are produced by combining the pressing and firing operations. Both uniaxial and isostatic methods are used.
  96. 96. • Slip Casting - This is where slip, liquid clay, is poured into a plaster mould. The water in the slip is drawn out of the slip, leaving an inside layer of solid clay. When this is thick enough, the excess slip can be removed from the mould. When dry, the solid clay can then also be removed. The slip used in slip casting is often liquified with a substance that reduces the need for additional water to soften the slip; this prevents excessive shrinkage which occurs when a piece containing a lot of water dries.
  97. 97.  Slip Casting
  98. 98. • Extrusion - is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section. The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections, and to work materials that are brittle, because the material only encounters compressive and shear stresses. It also forms finished parts with an excellent surface finish.
  99. 99. PRESSED GLASS PROCESSING  Pressed glass, which offers better control of the glass’s density than blowing, was the first glass to be manufactured on a large scale with the invention of a glass-pressing machine in the U.S. in the 1920s. This worked by taking the molten glass from the furnace and dividing it up into small sections. These would be placed in molds made of iron or brass. A plunger would press the glass down into the mold, and after a few seconds it was ready.
  100. 100. BLOW MOLDING o To blow glass, a blob of molten glass is placed at the end of a long, hollow iron blowpipe. Air is blown in and causes the glass to form into a pear-shaped bulb, which is then rolled on an oiled slab, shaped with tools and sometimes re-blown into a mold. To keep the glass from hardening during this process, it is periodically re-heated in small ovens. If the glass is to be engraved, copper wheels are used, and if it is to be etched, hydrofluoric acid does the job. o For glass bottles, a molten glass bubble is employed. It is placed in a mold, and the air pressure in the bubble forces the glass against the side of the mold. Once the glass cools and hardens, the mold is opened and a newly-made glass bottle removed.
  101. 101. BLOW MOLDING
  102. 102. Thermal Treatments  Drying and Binder Removal ◦ The purpose of drying ceramics is to remove water from the plastic ceramic body before it is fired at higher temperature. Generally, drying to remove water is carried out at or below 100 degrees Celsius and can take as long as 24 hrs. for a large ceramic part. The bulk of organic binders can be removed from ceramic parts by heating in the range of 200 to 300 degrees Celsius, although some hydrocarbon residues may require heating to much higher temperature. Batch Kiln
  103. 103.  Vitrification - process which takes place during the firing of some ceramic materials whereby the glass phase liquefies and fills the pore spaces in the material. This liquid glass phase may also react with some of the remaining solid refractory material. Upon cooling, the liquid phase solidifies to form a vitreous or glassy matrix that bonds the unmelted particles together. Ceramic Product after Vitrification Process
  104. 104.  Sintering - a process by which small particles of a material are bonded together by solid-state diffusion - results in the transformation of a porous compact into a dense, coherent product - commonly used to produce ceramic shapes made of, for example, alumina, beryllia, ferrites, and titanates.
  105. 105. Summary ◦ The term "ceramic" once referred only to clay-based materials. However, new generations of ceramic materials have tremendously expanded the scope and number of possible applications. ◦ Ceramic materials are inorganic compounds, usually oxides, nitrides, silicates or carbides. The bonding is very strong--either ionic or network covalent. Many adopt crystalline structures, but some form glasses. The properties of the materials are a result of the bonding and structure. ◦ The processing of crystalline ceramics follows the basic steps that have been used for ages to make clay products. The materials are selected, prepared, formed into a desired shape, and sintered at high temperatures. Glasses are processed by pouring in a molten state, working into shape while hot, and then cooling. New methods such as chemical vapor deposition and sol-gel processing are presently being developed.
  106. 106. Summary ◦ Ceramics can withstand high temperatures, are good thermal insulators, and do not expand greatly when heated. ◦ Glasses are transparent, amorphous ceramics that are widely used in windows, lenses, and many other familiar applications. Light can induce an electrical response in some ceramics, called photoconductivity. ◦ Ceramics are strong, hard, and durable. This makes them attractive structural materials ◦ Ceramics vary in electrical properties from excellent insulators to superconductors. Thus, they are used in a wide range of applications. ◦ Ceramics has advanced far beyond its beginnings in clay pottery. Ceramic tiles cover the space shuttle as well as our kitchen floors. Ceramic electronic devices make possible high-tech instruments for everything from medicine to entertainment. Clearly, ceramics are our window to the future.