Chapter 18 Ceramics, Glasses, & Superconductors: Processing and Equipment

CHARACTERISTICS OF CERAMICS AND GLASS 1. HIGH TEMPERATURE STRENGTH 2 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

PROCESSING METHODS FOR CERAMICS 1. Crushing materials the raw 2 PROCESSING METHODS FOR CERAMICS 1. Crushing materials the raw 2. Shaping 3. Drying 4. Finishing

PROCESSING METHODS FOR GLASSES 1 PROCESSING METHODS FOR GLASSES 1. Mixing and melting the raw materials in a furnace 2. Shaping into molds

FIGURE 18. 1 Examples of (a) glass parts and (b) ceramic parts FIGURE 18.1 Examples of (a) glass parts and (b) ceramic parts. Source: (a) Courtesy of Commercial Optical Manufacturing, Inc. (b) Courtesy of Kyocera.

SHAPING OF CERAMICS

TABLE 18.1 General Characteristics of Ceramics Processing

FIGURE 18.2 Processing steps involved in making ceramic parts.

ADDITIVES 1. Binder 2. Lubricant to reduce friction between particles 3. Wetting agent to improve mixing 4. Plasticizer to make the mix more plastic and easy to shape 5. Agents to control foaming

SHAPING PROCESSES FOR CERAMICS 1. Casting  2. Plastic forming 3 SHAPING PROCESSES FOR CERAMICS 1. Casting  2. Plastic forming 3. Pressing

FIGURE 18. 3 Sequence of operations in slip casting a ceramic part 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 OPERATIONS 1. Grinding 2. Lapping and honing 3 FINISHING OPERATIONS 1. Grinding 2. Lapping and honing 3. Ultrasonic machining 4. Drilling 5. Laser beam machining

PRODUCTS 1. Flat sheets 2. Rods and tubes 3 PRODUCTS 1. Flat sheets 2. Rods and tubes 3. Discrete products: bottles vases and eye glasses 4. Glass fibers

FORMING AND SHAPING OF GLASS

FLAT SHEETS 1. Float method 2. Drawing process

FIGURE 18.7 The float method of forming sheet glass.

FIGURE 18.8 (a) Drawing process for drawing sheet glass from a molten bath. (b) Rolling process. Source: After W.D. Kingery.

TUBING AND RODS

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 FIBERS Continuous glass fibers are drawn through multiple orifices

TECHNIQUES FOR STRENGTHENING AND ANNEALING GLASS THERMAL TEMPERING the surfaces of hot glass are cooled rapidly by a blast of air residual compressive stresses develop at the surface interior part develosp tensile residual stresses Due to the high amount of energy stored in residual stresses, tempered glass shatters into numerous pieces when broken Lops tensile sile stres

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 GLASS Consists of two pieces of flat glass with a thin sheet of tough plastic in between When it cracks the pieces are held together by the plastic sheet (less hazardous than tempered glass)