1. Today’s objectives-glass and clay products and processing What are standard glass additives, and how do they effect structure and properties? How do specific volume and viscosity vary with temperature? How are glass sheets and containers prepared? Why are annealing and tempering important for glass? What are the steps in processing clays? What is slip, and what is hydroplasticity? Describe casting Describe extruding Describe drying Describe firing Primary glass resource: Corning Museum of Glass (www.cmog.org)

5. GLASS STRUCTURE • Basic Unit: • Glass is amorphous • Amorphous structure occurs by adding impurities (Na + ,Mg 2+ ,Ca 2+ , Al 3+ ) • Impurities: interfere with formation of crystalline structure. • Quartz is crystalline SiO 2 : (soda glass) Adapted from Fig. 12.11, Callister, 6e .

7. GLASS PROPERTIES • Specific volume (1  ) vs Temperature (T): • Glasses : --do not crystallize --spec. vol. varies smoothly with T -- Glass transition temp , T g • Crystalline materials : --crystallize at melting temp, T m --have abrupt change in spec. vol. at T m Adapted from Fig. 13.5, Callister, 6e .

9. GLASS VISCOSITY VS T AND IMPURITIES • Viscosity decreases with T - (sample flows easier) • Impurities lower T deform • Viscosity : --relates shear stress & velocity gradient: --has units of (Pa-s) Adapted from Fig. 13.6, Callister, 6e . (Fig. 13.6 is from E.B. Shand, Engineering Glass , Modern Materials, Vol. 6, Academic Press, New York, 1968, p. 262.) Tmelt

13. HEAT TREATING GLASS • Annealing : --removes internal stress caused by uneven cooling. Chemical tempering is also possible. • Tempering : --puts surface of glass part into compression --suppresses growth of cracks from surface scratches. --sequence:

14. Fabricating Glass in other shapes • Pressing: GLASS FORMING • Blowing: Adapted from Fig. 13.7, Callister, 6e . (Fig. 13.7 is adapted from C.J. Phillips, Glass: The Miracle Maker , Pittman Publishing Ltd., London.)

17. 7000 ‘soldiers’ thus far discovered

20. Ingredients Kaolin: is a clay mineral with the chemical composition Al 2 Si 2 O 5 (OH) 4 . It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra. Feldspar: is the name of a group of rock-forming minerals which make up as much as 60% of the Earth's crust. Feldspars crystallize from magma in both intrusive and extrusive rocks, and they can also occur as compact minerals, as veins, and are also present in many types of metamorphic rock. Rock formed entirely of plagioclase feldspar (see below) is known as anorthosite. Feldspars are also found in many types of sedimentary rock. Quartz: belongs to the hexagonal rhombohedral crystal system, and is made up of silica (SiO 2 ) tetrahedra.

22. What are basic ceramics made of? • Clay (inexpensive) • Milling and screening: achieve desired particle size. • Adding water to the clay particles produces a "slip:" --layered structure --allows material to shear easily along weak van der Waals bonds Hydroplastic --enables extrusion --enables slip casting --enables pottery wheel (Ghost) • Structure of Kaolinite Clay Adapted from Fig. 12.14, Callister 6e . (Fig. 12.14 is adapted from W.E. Hauth, "Crystal Chemistry of Ceramics", American Ceramic Society Bulletin , Vol. 30 (4), 1951, p. 140.)