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Ceramics.

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Presentation on theme: "Ceramics."— Presentation transcript:

1 Ceramics

2 Aluminum vs. Alumina Demo
Sketch the setup of the demo Mass of aluminum_____ Mass of Alumina_____ Describe WHAT you observed Aluminum vs. Alumina Lab 2 – C Aluminum will have the greatest thermal conductivity Aluminum will have the greatest electrical conductivity Alumina is less dense than aluminum – mass each rod and compute the density weight g/volume ml(use water displacement) Aluminium oxide is an amphoteric oxide of aluminium with the chemical formula Al2O3. It is also commonly referred to as alumina or aloxite[2] in the mining, ceramic and materials science communities. It is produced by the Bayer process from bauxite. Its most significant use is in the production of aluminium metal, although it is also used as an abrasive due to its hardness and as a refractory material due to its high melting point 2

3 Aluminum vs. Alumina Demo WHY it Happened
Aluminum= Al=metal Aluminum Oxide, Alumina, Al2O3 = ceramic ceramics have higher melting points than pure metals alumina has a melting point of 2054° C aluminum melts at 660° C ceramics don’t conduct electricity

4 What are Ceramics Ceramics are non-metallic materials that are typically produced using clays and other minerals from the earth The word ceramic, derives its name from the Greek word, keramos, meaning “pottery” This word was derived from an older root, meaning “to burn".

5 Traditional Categories of Ceramics
whiteware dinnerware, floor and wall tile, pottery, decorative ceramics Glass flat glass (windows), container glass (bottles), pressed and blown glass (dinnerware), glass fibers (home insulation) Abrasives Natural (garnet, diamond, etc.) and synthetic (silicon carbide, diamond, fused alumina, etc.) abrasives are used for grinding Structural, Clay Products Brick, sewer pipe, roofing tile, clay floor and wall tile (i.e., quarry tile), flue linings Cement Concrete roads, bridges, buildings, dams, residential sidewalks, bricks/block Refractories Brick and monolithic products used in iron and steel, non-ferrous metals, glass, cements, ceramics, energy conversion, petroleum, and chemicals industries, kiln furniture used in various industries Of a material) able to resist high temperature, for example ceramics made from clay, minerals, or other earthy materials. Furnaces are lined with refractory materials such as silica and dolomite. Alumina (aluminium oxide) is an excellent refractory, often used for the bodies of spark plugs. Titanium and tungsten are often called refractory metals because they are temperature resistant. 5

6 Advanced Categories of Ceramics
Product Area Product Aerospace space shuttle tiles, thermal barriers, high temperature glass windows, fuel cells Consumer Uses glassware, windows, pottery, Corning® ware, magnets, dinnerware, ceramic tiles, lenses, home electronics, microwave transducers Automotive catalytic converters, ceramic filters, airbag sensors, ceramic rotors, valves, spark plugs, pressure sensors, thermistors, vibration sensors, oxygen sensors, safety glass windshields, piston rings Medical (Bioceramics) orthopedic joint replacement, prosthesis, dental restoration, bone implants Military structural components for ground, air and naval vehicles, missiles, sensors Computers insulators, resistors, superconductors, capacitors, ferroelectric components, microelectronic packaging Other Industries bricks, cement, membranes and filters, lab equipment Communications fiber optic/laser communications, TV and radio components, microphones

7 Metals Ceramics compound metal + Nonmetal crystalline ionic bonding
Type of Matter Element or mixture compound Type of Elements metals metal + Nonmetal Type of Structure Crystalline crystalline Type of Bonding Metallic bonding ionic bonding 1. MECHANICAL PROPERTIES- they are crystalline or amorphous and are usually covalently bonded or iconic substances. Ceramic materials also show plastic deformations. 2. ELECTRICAL PROPERTIES- they are semi conductors and most of them are transitional metal oxides. However under extremely low temperatures some ceramics become superconductors. The electrical properties of semimetals are partway between those of metals and semiconductorsThe electrical properties of semimetals are partway between those of metals and semiconductors. The classic semimetallic elements are arsenicThe electrical properties of semimetals are partway between those of metals and semiconductors. The classic semimetallic elements are arsenic, antimonyThe electrical properties of semimetals are partway between those of metals and semiconductors. The classic semimetallic elements are arsenic, antimony, and bismuth. 7

8 Ceramic Structures crystalline ionic bonds Types of Structure 37 – S
Use the BB board to demo this concept. Crystalline solids are arranged in fixed geometric patterns or lattices. Examples of crystalline solids are ice, methanol, and sodium chloride (table salt). They have an orderly arranged units and are practically incompressible. Crystalline solids also show a definite melting point and so they pass rather sharply from solid to liquid state. There are various crystalline forms which are divided into six crystal systems or shapes. They are cubic, tetragonal, hexagonal, rhombic, monoclinic, and triclinic. The units that constitute these systems can be atoms, molecules, or ions. Ionic and atomic crystals are hard and brittle with high melting points. Molecular crystals are soft and have low melting points. Metallic crystals are composed of positively charged ions in a field of electron gas or freely moving electrons. Metals are good conductors of electricity because of the free movement of electrons in the lattice. Amorphous solids are solids with random unoriented molecules. Examples of amorphous solids are glass and plastic. They are considered super cooled liquids in which the molecules are arranged in a random manner some what as in the liquid state. Amorphous solids also unlike crystalline solids do not have definite melting points. crystalline ionic bonds 8

9 Crystalline-Ionic Bonding
Remember ionic bonds are metals and nonmetals transfer of electrons from metals to nonmetals

10 Why Bonding in Ceramics Matter
1. Ceramics are poor conductors of heat & electricity have no free valence electrons that roam like metallic bonds do 2. Ceramics are brittle because the crystalline structure does not allow atoms to easily shift positions under stress.

11 Why Bonding in Ceramics Matter
3. Ceramics are resistant to corrosion. The ionic bonds occur when metals lose electrons to nonmetals so they can be thought of as already “corroded” metals 4. Ceramics have higher melting points due to strong ionic bonds

12 Metals Ceramics Glass compound mixtures of compounds metal + Nonmetal
Type of Matter Element or mixture compound mixtures of compounds Type of Elements metals metal + Nonmetal nonmetals Type of Structure Crystalline crystalline amorphous Type of Bonding Metallic bonding ionic bonding network covalent bond 1. MECHANICAL PROPERTIES- they are crystalline or amorphous and are usually covalently bonded or iconic substances. Ceramic materials also show plastic deformations. 2. ELECTRICAL PROPERTIES- they are semi conductors and most of them are transitional metal oxides. However under extremely low temperatures some ceramics become superconductors. The electrical properties of semimetals are partway between those of metals and semiconductorsThe electrical properties of semimetals are partway between those of metals and semiconductors. The classic semimetallic elements are arsenicThe electrical properties of semimetals are partway between those of metals and semiconductors. The classic semimetallic elements are arsenic, antimonyThe electrical properties of semimetals are partway between those of metals and semiconductors. The classic semimetallic elements are arsenic, antimony, and bismuth. 12

13 Electrical conductivity
PROPERTY METALS CERAMICS Atomic structure Crystalline crystalline Melting point Low to High high to very high Thermal conductivity Good poor Electrical conductivity Optical Properties Opaque opaque Hardness Soft to hard harder Workability Ductile and malleable brittle Tensile Strength High low

14 Oxidize easily (reactivity series) resistant to corrosion
PROPERTY METALS CERAMICS/GLASS Density Higher less Impact Strength Good poor Corrosion Oxidize easily (reactivity series) resistant to corrosion

15 Ceramic vs. Glass Structures
Types of Structure 37 – S Use the BB board to demo this concept. Crystalline solids are arranged in fixed geometric patterns or lattices. Examples of crystalline solids are ice, methanol, and sodium chloride (table salt). They have an orderly arranged units and are practically incompressible. Crystalline solids also show a definite melting point and so they pass rather sharply from solid to liquid state. There are various crystalline forms which are divided into six crystal systems or shapes. They are cubic, tetragonal, hexagonal, rhombic, monoclinic, and triclinic. The units that constitute these systems can be atoms, molecules, or ions. Ionic and atomic crystals are hard and brittle with high melting points. Molecular crystals are soft and have low melting points. Metallic crystals are composed of positively charged ions in a field of electron gas or freely moving electrons. Metals are good conductors of electricity because of the free movement of electrons in the lattice. Amorphous solids are solids with random unoriented molecules. Examples of amorphous solids are glass and plastic. They are considered super cooled liquids in which the molecules are arranged in a random manner some what as in the liquid state. Amorphous solids also unlike crystalline solids do not have definite melting points. crystalline ionic bonds amorphous network covalent bonds 15

16 Glass-Covalent Bonds To Remember about covalent bonds:
made of all nonmetals sharing of electrons covalent network bonds occurs when covalent bonds are in large network throughout the material

17 General Glass Info Doesn’t have a definite melting point-just gradually softens b/c glass is amorphous very viscous Rather poor conductor of electricity and heat resistant to chemical attack useful for food containers and laboratory apparatus

18 Glass Bending / Rods

19 Fiber Optics and Internal Reflection
Internal Reflection-Light will reflect off the side walls of glass fiber Fiber Optics- usually glass fiber used for communication used instead of metal wires b/c signals travel with less loss & are not disturbed by electromagnetic interference use lasers as the light source

20 MAIN GLASS INGREDIENTS
CATEGORY PURPOSE INGREDIENT Glass Former backbone of network SiO2 (silica)-most common could also be oxides of B, Ge, P, As, and V Modifier lowers melt temp makes easier to work with Na2O (soda) & CaO (lime) Intermediate gives specific properties oxides of Al, Pb, Sn, Zn,B Pb-makes it have high refractive index

21 Main Ingredients for Glass
Silica(silicon dioxide, SiO2) the chief constituent of sand quartz-silica in crystalline form=mineral fused silica=silica in amorphous form=glass However, fused silica is not used for commercial glass products for 2 reasons: it has a super high melting point (1650C or 3000F) when molten it has a very high viscosity and is difficult to form.

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23 The amorphous structure of glassy Silica (SiO2)
The amorphous structure of glassy Silica (SiO2). No long range order is present, however there is local ordering with respect to the tetrahedral arrangement of Oxygen (O) atoms around the Silicon (Si) atoms.

24 Other Ingredients in Glass
Fining agents small amounts of other compounds added to help get rid of gas bubbles formed during melting process. Many other ingredients -give specific colors or other properties. For example, iron oxides can be added to give glass a green color and help absorb heat

25 Glass Bead on a Wire blue Oxidizing (outer portion) Reducing
Nichrome blue Copper Blue/green Cu 2+ ions Reducing (tip inner cone) Glass Bead on Wire 34 – C A small loop is made in the end of a nichrome wire (as used in the flame testA small loop is made in the end of a nichrome wire (as used in the flame test) and heated in a BunsenA small loop is made in the end of a nichrome wire (as used in the flame test) and heated in a Bunsen flame until red hot. It is then dipped into powdered boraxA small loop is made in the end of a nichrome wire (as used in the flame test) and heated in a Bunsen flame until red hot. It is then dipped into powdered borax, and the adhering solid is held in the hottest part of the flame where it swells up as it loses its water of crystallizationA small loop is made in the end of a nichrome wire (as used in the flame test) and heated in a Bunsen flame until red hot. It is then dipped into powdered borax, and the adhering solid is held in the hottest part of the flame where it swells up as it loses its water of crystallization and then shrinks, forming a colourless, transparent glass-like bead (a mixture of sodium metaborateA small loop is made in the end of a nichrome wire (as used in the flame test) and heated in a Bunsen flame until red hot. It is then dipped into powdered borax, and the adhering solid is held in the hottest part of the flame where it swells up as it loses its water of crystallization and then shrinks, forming a colourless, transparent glass-like bead (a mixture of sodium metaborate and boric anhydride), 25

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28 Most Common Types of Glass
Glass Type Ingredients Uses Advantages Disadvantages Soda-lime (flint) (most common) Silica (SiO2) Soda (Na2O) Lime (CaO) Windows, bottles, etc. Low price, Forms shapes easily Low thermal shock resistance Borosilicate Alumina (Al2O3) Boron oxide (B2O3) Lab glassware Cookware Lamp bulbs (Pyrex) Withstands thermal shock better and higher temps More expensive, Harder to work Lead-alkali (lead crystal) Sodium oxide Lead oxide Art glass, Expensive glassware Sparkle, High electrical resistance Toxicity, Doesn’t w/stand thermal shock or high temp

29 Types of Glass Soda Lime glass (cheap) windows 696c
Softening temp Soda Lime glass (cheap) windows c Borosilicate (better) beakers PYREX 780c Fused Silica (best) c SiO2 Pure Silica – components are added to change the properties (lower melting points, change refractive index, absorption of head) Soda-lime glass is prepared by melting the raw materialsis prepared by melting the raw materials, such as sodais prepared by melting the raw materials, such as soda, limeis prepared by melting the raw materials, such as soda, lime, silicais prepared by melting the raw materials, such as soda, lime, silica, aluminais prepared by melting the raw materials, such as soda, lime, silica, alumina, and small quantities of fining agents (e.g., sodium sulfateis prepared by melting the raw materials, such as soda, lime, silica, alumina, and small quantities of fining agents (e.g., sodium sulfate, sodium chlorideis prepared by melting the raw materials, such as soda, lime, silica, alumina, and small quantities of fining agents (e.g., sodium sulfate, sodium chloride) in a glass furnace at temperatures locally up to 1675°C. Its appearance end on is a bluish tint. Borosilicate glass is a type of glass is a type of glass with the main glass-forming constituents silica is a type of glass with the main glass-forming constituents silica and boron oxide is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are most well known for having very low coefficient of thermal expansion (~ 3 x 10-6 / C at 20oC), making them resistant to thermal shockC), making them resistant to thermal shock, more so than any other common glass. Borosilicate glass was first developed by German glassmaker Otto Schott in the late 19th century[1] and sold under the brand name "Duran" in After Corning Glass Works and sold under the brand name "Duran" in After Corning Glass Works introduced Pyrex and sold under the brand name "Duran" in After Corning Glass Works introduced Pyrex in 1915, it became a synonym for borosilicate glass in the English-speaking world (however, since 1998 Pyrex kitchen brand is no longer made of borosilicate but of soda-lime glass[2]). Most borosilicate glass is clear. Fused Silica - The extremely low coefficient of thermal expansion accounts for its remarkable ability to undergo large, rapid temperature changes without cracking.Specially prepared fused silica is also the key starting material used to make optical fiber for telecommunications. Because of its strength and high melting point (compared to ordinary glassBecause of its strength and high melting point (compared to ordinary glass), fused silica is used as the envelope of halogen lamps, which must operate at a high envelope temperature to achieve their combination of high brightness and long life. 29

30 Thermal Shock Demo

31 Thermal Shock Glass tends to shatter or crack when exposed to extreme temps too quickly The outside will cool/contract or heat/expand quicker than the inside A lot of stress is put on the glass and it fails

32 2 Factors affecting Thermal Shock
Thermal Expansion the greater the coefficient of thermal expansion the more likely thermal shock 2. Thermal Conductivity The more the a material conducts heat, the more evenly it is distributed→ the less chance of thermal shock

33 Coefficient of Thermal Expansion
Thermal Shock Coefficient of Thermal Expansion: how much a material will expand when heated by 1 degree Material Coefficient of Thermal Expansion Fused Silica Glass Borosilicate Glass 6 X 10-7 Aluminosilicate Glass 33 X 10-7 Porcelain 44 X 10-7 Soda-Lime Glass 60 X 10-7 Steel 85 x 10-7 Aluminum 110 X 10-7

34 Material Aluminum metal 23.6 247 Copper metal 16.5 398 Alumina 8.8
Coefficient of Linear Expansion 1/ ° Cx10-6 Thermal Conductivity (W/m K) Aluminum metal 23.6 247 Copper metal 16.5 398 Alumina 8.8 30.1 Fused Silica 0.5 2.0 Soda-Lime glass 9.0 1.7 Polyethylene 60-220 0.38 Polystyrene 50-85 .13

35 Based on this information predict which glass is less likely to thermal shock
 Watch Video: ?v=2kxTtnPGHSo (2 ½ minutes)

36 Processing—Heat Treating
Annealing stresses build up in glass objects as they are cooled b/c glass can cool unevenly - weakens glass and may cause spontaneous fracture. glass is reheated in ovens called lehrs, and then allowed to cool slowly to relieve the stresses Annealing Video (3 minutes): Q&list=PLAEC682A8C50D1FF8&index=8

37 Processing: Heat Treating
2. Tempering (2 minutes) glass is heated to just below the softening temperature and is quenched to intentionally stress the entire surface uniformly. - outside is under compression - cooled/contracting - inside of glass is under tension- hot/ expanding Advantages - much tougher than regular glass - when breaks it breaks into tiny pieces for safety Disadvantages - Tempered glass cannot be cut or drilled. - weak on its edges Video:

38 Cool Glass Videos! Rupert’s drop video (7 minutes)
Glass Blowing Compilation (14 minutes) RikrwY


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