1 2 lecture ceramic engineering me
- 2. MM-532 Ceramic Engineering • Crystal Structures and Origin of Ceramics, Physical and Thermal properties of Ceramics, Structure of Ceramics, Silicate Ceramics, Imperfections in Ceramics, Ceramic phase Diagrams, Mechanical Properties of Ceramic Materials. Stress-Strain behaviour, Miscellaneous Mechanical Considerations, Processing of ceramic Powders, Powder Characterization and data analysis, Sintering Thermodynamics and Kinetics, Novel Sintering Techniques, Characterization of Sintered Products, Study of Transition Alumina and Transformation Toughening in Ceramics Development Fabrication and Processing of Carbides and Nitrides, Characterization of Carbide and Nitride Ceramics. 40 Marks: Sessional & 60 Marks: Final paper
- 3. Ceramic Science and Engineering When you hear the word “ceramics,” people usually think of an image of pottery or space shuttle tiles. What many people don’t realize is that ceramics and ceramic engineering play an important role almost everywhere you look and sometimes where you can’t look. Besides everyday objects, ceramics are helping computers and other electronic devices operate, improving people’s health in various ways, providing global telecommunications, and protecting soldiers during combat.
- 4. In the most simple of terms, ceramics are inorganic, nonmetallic materials. They are typically crystalline in nature (have an ordered structure) and are compounds formed between metallic and nonmetallic elements such as aluminum and oxygen (alumina, Al2O3), calcium and oxygen (CaO), and silicon and nitrogen (silicon nitride, Si3N4). In broader terms, ceramics also include glass (which has a non-crystalline or amorphous random structure), enamel (a type of glassy coating), glass-ceramics (a glass containing ceramic crystals), and inorganic cement-type materials (cement, plaster and lime). However, as ceramic technology has developed over time, the definition has expanded to include a much wider range of other compositions used in a variety of applications. The word “ceramic” is traced back to the Greek term keramos, meaning potter’s clay or pottery. Keramos, in turn, is related to an older Sanskrit root, meaning “to burn.” Ceramus or Keramos was also an ancient city on the north coast of the Aegean Sea in what is present-day Turkey.
- 5. Structural Clay Products Brick, sewer pipe, roofing tile, clay floor and wall tile whitewares Dinnerware, floor and wall tile, electrical porcelain, decorative ceramics Refractories Brick and monolithic products used in iron and steel, non-ferrous metals, glass, cements, ceramics, energy conversion, petroleum, and chemicals industries, kiln furniture Glasses Flat glass (windows), container glass (bottles), pressed and blown glass (dinnerware), glass fibers (home insulation) Cements Concrete roads, bridges, buildings, dams, sidewalks, bricks/blocks Abrasives Natural and Synthetic abrasives Automotive cam rollers, fuel pump rollers, brakes, clutches, spark plugs, sensors, filters, windows, thermal insulation, emissions control, heaters, igniters, glass fiber composites for door chassis Aerospace Thermal insulation, space shuttle tiles, wear components, combustor liners, turbine blades/rotors, fire detection feedthrus, thermocouple housings, aircraft instrumentation and control systems, satellite positioning equipment, ignition systems, instrument displays and engine monitoring equipment, nose caps, nozzle jet vanes, engine flaps Chemical Thermocouple protection tubes, tube sheet boiler ferrules, catalysts, catalyst supports, pumping components, rotary seals Areas of Specialization or Branches of Ceramics Boiler Tube Ferrules There are two major categories of glasses and ceramics: traditional and advanced
- 6. Coatings Engine components, cutting tools, industrial wear parts, biomedical implants, anti- reflection, optical, self-cleaning coatings for building materials Electrical/ Electronic Capacitors, insulators, substrates, integrated circuit packages, piezoelectric, transistor dielectrics, magnets, cathodes, superconductors, high voltage bushings, antennas, sensors, accelerator tubes for electronic microscopes, substrates for hard disk drives Environmental Solid oxide fuel cells, gas turbine components, measuring wheels/balls for check valves (oilfields), nuclear fuel storage, hot gas filters (coal plants), solar cells, heat exchangers, isolator flanges for nuclear fusion energy research, solar-hydrogen technology, glass fiber reinforcement
- 7. Duties and Responsibilities Ceramic Engineers might be expected to carry out the following….. • Supervise or test chemical , physical, or electrical properties on ceramic substances • Analyze test results • Seek information on firing, processing, and forming new ceramic products out of inorganic and raw materials • Figuring out different uses for the ceramic materials • Controlling or directing other workers activities • Rating information • Taking accurate and precise measurements • Think logically • Comparing different characteristics of useable materials • Demonstrate a variety of high level mathematical skills Responsibilities: Duties:
- 8. Greatest Engineering Achievements of the 20th Century Achievement How Ceramics Contribute: 1. Electrification Electrical insulators for power lines, insulators for industrial/household applications, glass light bulbs 2. Automobile Engine sensors, catalytic converters, spark plugs, windows, engine components, electrical devices 3. Airplane Anti-fogging/freezing glass windows, jet engine components, electronic components
- 9. 4. Safe water supply and treatment Filters/membranes 5. Electronics Substrates and IC packages, capacitors, piezoelectrics, insulators, magnets, superconductors 6. Radio and television Glass tubes (CRTs), glass faceplate, phosphor coatings, electrical components, magnets 7. Agricultural mechanization Refractories for melting and forming of ferrous and non-ferrous metal components 8. Computers Electrical components, magnetic storage, glass for computer monitors
- 10. 9. Telephone Electrical components, glass optical fibers 10. Air conditioning and refrigeration Glass fiber insulation, ceramic magnets 11. Interstate highways Cement for roads and bridges, glass microspheres used to produce reflective paints for signs and road lines. 12. Space exploration Space shuttle tile, high-temperature resistant components, ceramic ablation materials, electromagnetic and transparent windows, electrical components, telescope lenses
- 11. 13. Internet Electronic components, magnetic storage, computer monitor glass 14. Imaging: X-rays to film Piezoceramic transducers for ultrasound diagnostics, sonar detection, ocean floor mapping and more, ceramic scintillator for X-ray computed tomography (CT scans), telescope lenses, glass monitors, phosphor coatings for radar and sonar screens 15. Household appliances Porcelain enamel coatings for major appliances, glass fiber insulation for stoves and refrigerators, electrical components, glass-ceramic stove tops, spiral resistance heaters for toasters, ovens and ranges 16. Health technologies Replacement joints, heart valves, bone substitutes, hearing aids, pacemakers, teeth replacements/braces, transducers for ultrasound diagnostics, scintillators for X-ray computed tomography (CT scans), cancer treatments
- 12. 17. Petroleum and natural gas technologies Ceramic catalysts, refractories, packing media for petroleum and gas refinement, cement and drill bits for well drilling 18. Lasers and fiber optics Glass optical fibers, fiber amplifiers, laser materials, electronic components 19. Nuclear technologies Fuel pellets, control rods, high- reliability seats and valves, nuclear waste containment 20. High-performance materials Including advanced ceramics for their excellent wear, corrosion and high temperature resistance; high stiffness; high melting point; high compressive strength and hardness; and wide range of electrical, magnetic, and optical properties
- 15. Structure and Properties of Ceramics Ceramics usually have a combination of stronger bonds called ionic (occurs between a metal and nonmetal and involves the attraction of opposite charges when electrons are transferred from the metal to the nonmetal); • The strength of an ionic bond depends on the size of the charge on each ion and on the radius of each ion. • The greater the number of electrons being shared, is the greater the force of attraction, or the stronger the covalent bond. • These types of bonds result in high elastic modulus and hardness, high melting points, low thermal expansion, and good chemical resistance. On the other hand, ceramics are also hard and often brittle (unless the material is toughened by reinforcements or other means), which leads to fracture.
- 24. Oxide nickel-zinc ferrite representation, with stoichiometry Ni0.5Zn0.5Fe2O4 with structure type inverse spinel.
- 40. Property Ceramic Metal Polymer Hardness Very High Low Very Low Elastic modulus Very High High Low High temperature strength Thermal expansion High Low Very Low Ductility Low High High Corrosion resistance High Low Low Wear resistance High Low Low Electrical conductivity Depends on material High Low Density Low High Very Low Thermal conductivity Depends on material High Low Magnetic Depends on material High Very Low General Comparison of Materials
- 43. Zirconium dioxide is one of the most studied ceramic materials. Pure ZrO2 has a monoclinic crystal structure at room temperature and transitions totetragonal and cubic at increasing temperatures. The volume expansion caused by the cubic to tetragonal to monoclinic transformation induces very large stresses, and will cause pure ZrO2 to crack upon cooling from high temperatures. Several different oxides are added to zirconia to stabilize the tetragonal and/or cubic phases: magnesium oxide (MgO), yttrium oxide, (Y2O3), calcium oxide (CaO), and cerium(III) oxide (Ce2O3), amongst others. Zirconia is very useful in its 'stabilized' state. In some cases, the tetragonal phase can be metastable. If sufficient quantities of the metastable tetragonal phase is present, then an applied stress, magnified by the stress concentration at a crack tip, can cause the tetragonal phase to convert to monoclinic, with the associated volume expansion. This phase transformation can then put the crack into compression, retarding its growth, and enhancing the fracture toughness. This mechanism is known as transformation toughening, and significantly extends the reliability and lifetime of products made with stabilized zirconia.
- 45. Fully Stabilized Zirconia Generally, addition of more than 16 mol% of CaO (7.9 wt%), 16 mol% MgO (5.86 wt%), or 8 mol% of Y2O3 (13.75 wt%), into zirconia structure is needed to form a fully stabilized zirconia. Its structure becomes cubic solid solution. Its structure becomes cubic solid solution, which has no phase transformation from room temperature up to 2,500 ° C. As a good ceramic ion conducting materials, fully yttria stabilized Zirconia (YSZ) has been used in oxygen sensor and solid oxide full cell (SOFC) applications. The SOFC applications have recently been attracting more worldwide attention, due to their high energy transfer efficient and environment concerns.