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Chapter 18 Ceramics, Glasses, & Superconductors: Processing and Equipment. CHARACTERISTICS OF CERAMICS AND GLASS 1. HIGH TEMPERATURE STRENGTH 2. HIGH HARDNESS 3. LOW ELECTRICAL CONDUCTIVITY 4. LOW THERMAL CONDUCTIVITY 5. RESISTANCE TO WEAR 6. RESISTANCE TO CORROSION.
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Chapter 18Ceramics, Glasses, & Superconductors: Processing and Equipment
CHARACTERISTICS OF CERAMICS AND GLASS1. HIGH TEMPERATURE STRENGTH2. HIGH HARDNESS3. LOW ELECTRICAL CONDUCTIVITY4. LOW THERMAL CONDUCTIVITY5. RESISTANCE TO WEAR6. RESISTANCE TO CORROSION
PROCESSING METHODS FOR CERAMICS1. Crushing materials the raw2. Shaping3. Drying4. Finishing
PROCESSING METHODS FOR GLASSES1. Mixing and melting the raw materials in a furnace2. Shaping into molds
FIGURE 18.1 Examples of (a) glass parts and (b) ceramic parts.Source: (a) Courtesy of Commercial Optical Manufacturing, Inc. (b) Courtesy of Kyocera.
FIGURE 18.2 Processing steps involved in making ceramic parts.
ADDITIVES1. Binder2. Lubricant to reduce friction between particles3. Wetting agent to improve mixing4. Plasticizer to make the mix more plastic and easy to shape5. Agents to control foaming
SHAPING PROCESSES FOR CERAMICS1. Casting 2. Plastic forming3. Pressing
FIGURE 18.3 Sequence of operations in slip casting a ceramic part. (a) Mold is assembled and plug attached; some plugs incorporate draining features; (b) slurry, mixed from ceramic particles, binder, and water, is poured into the mold; (c) the mold is inverted and the slurry is poured from the mold, leaving a thin coating over the mold cavity; (d) after an initial drying period, the slip is removed from the mold, and features such as parting lines and sprue lips are removed; and (e) the slip is ready to be dried and fired in an oven, to develop strength and hardness.
FIGURE 18.4 Production of ceramic sheets through the doctor-blade process.
FINISHING OPERATIONS1. Grinding2. Lapping and honing3. Ultrasonic machining4. Drilling5. Laser beam machining
PRODUCTS1. Flat sheets2. Rods and tubes3. Discrete products: bottles vases and eye glasses4. Glass fibers
FIGURE 18.8 (a) Drawing process for drawing sheet glass from a molten bath. (b) Rolling process. Source: After W.D. Kingery.
FIGURE 18.9 Manufacturing process for glass tubing; air is blown through the mandrel to keep the tube from collapsing; glass tubes for fluorescent bulbs are made by this method.
FIGURE 18.13 Centrifugal casting of glass; large telescope lenses and television-tube funnels are made by this process. Source: Based on data from Corning Glass Works.
GLASS FIBERSContinuous glass fibers are drawn through multiple orifices
TECHNIQUES FOR STRENGTHENING AND ANNEALING GLASSTHERMAL TEMPERINGthe surfaces of hot glass are cooled rapidly by a blast of airresidual compressive stresses develop at the surfaceinterior part develosp tensile residual stressesDue to the high amount of energy stored in residual stresses, tempered glass shatters into numerous pieces when broken
FIGURE 18.14 (a) The stages involved in inducing compressive surface residual stresses for improved strength. (b) Residual stresses in a tempered glass plate. Source: Courtesy of Corning Glass Works.
FIGURE 18.15 Schematic illustration of the powder-in-tube process.
LAMINATED GLASSConsists of two pieces of flat glass with a thin sheet of tough plastic in betweenWhen it cracks the pieces are held together by the plastic sheet (less hazardous than tempered glass)