Bruce Mayer, PE Registered Electrical & Mechanical Engineer BMayer@ChabotCollege

1. Engineering 45 CeramicApps/Processes Bruce Mayer, PE Registered Electrical & Mechanical EngineerBMayer@ChabotCollege.edu

2. Learning Goals – Ceramic Apps • The Classification of Ceramic Types • Review Several Ceramic-Material Applications • How Ceramic Processing Differs From That of Metals

3. Taxonomy of Ceramics Glasses Clay Refractories Abrasives Cements Advanced products ceramics -bricks for -optical -whiteware -sandpaper -composites engine high T - composite - bricks - cutting - structural - rotors (furnaces) reinforce - polishing - valves - containers - bearings - household -sensors • Ceramic Properties • Tmelt for GLASS is moderate, but large for other CERAMICS. • Small toughness, ductility; large elastic moduli & creep resistance • Applications: • High T, wear resistant, novel uses by charge neutrality • Fabrication • some glasses can be easily formed • other ceramics can not be formed or cast

4. Need a material to use in high temp furnaces Consider Silica (SiO2) - Alumina (Al2O3) system Phase diagram shows Tetrahedral Structures as Candidates: Mullite (3Al2O3•2SiO2), alumina (Al2O3), and crystobalite (form of SiO2) Most FireBrick is taken from the Mullite + Crystobalite Field 2200 3Al O -2 SiO 2 3 2 T(°C) mullite 20 00 Liquid alumina + L (L) 1800 mullite alumina crystobalite + L + + L 1600 mullite mullite + crystobalite 1400 0 2 0 4 0 6 0 8 0 100 Composition (wt% alumina) Application - Refractories

5. FireBrick Composition

6. Rod/Wire Drawing Dies need WEAR Resistant Properties DIAMOND Thin-Films are VERY Hard Die surface 4 µm polycrystalline diamond particles that are sintered on to a cemented tungsten carbide substrate. polycrystalline diamond helps control fracture and gives uniform hardness in all directions. Courtesy Martin Deakins, GE Superabrasives, Worthington, OH. Used with permission. Application – Die Blanks

7. Tools for Difficult Applications: Grinding: glass, tungsten carbide, other ceramics Cutting Si-wafers Oil Drilling (think rocks) Solutions: manufactured single crystal or polycrystalline diamonds in a metal or resin matrix. optional coatings (e.g., Ti to help diamonds bond to a Co matrix via alloying) polycrystalline diamonds self-sharpen by microfracturing along crystalline planes Application – Cutting Tools blades oil drill bits coated single crystal diamonds polycrystalline diamonds in a resin matrix. Photos courtesy Martin Deakins, GE Superabrasives, Worthington, OH. Used with permission.

8. Ex: Oxygen sensor: ZrO2 Principle: Make diffusion of ions fast for rapid response. Approach: Add Ca impurity to: increase O2- vacancies increase O2- diffusion Operation: voltage difference produced when O2- ions diffuse between external and references gases. 2+ Ca 2+ A Ca impurity 4+ removes a Zr and a 2 - O ion. sensor gas with an reference unknown, higher gas at fixed 2- O oxygen content oxygen content diffus ion - + voltage difference produced! Application – Sensors

9. Comb Drive Electrostatic Engine Lead Wire MEMS in Motion

10. Ceramic Fabrication Methods-I GLASS FORMING PARTICULATE CEMENTATION FORMING • Pressing: • Fiber drawing: • Blowing:

11. Basic Unit 4- Si0 tetrahedron 4 4+ Si + Na 2 - O 4+ Si 2 - O SodaLimeGlass Recall Glass Structure • Glass is AMORPHOUS • Amorphous structure occurs by adding impurities; e.g., Na+, Mg2+ ,Ca2+, Al3+ • Impurities interfere with the formation of thecrystallinestructure • Quartz = Crystalline SiO2

12. Specific volume (1/ρ) vs Temperature (T): Glass Properties • Crystalline materials: • crystallize at melting temp, Tm • have abrupt change in spec. vol. at Tm • Glasses: • do not crystallize • Spec. vol. varies smoothly with T • Glass transition temp, Tg → Chg in Slope

13. Viscosity: relates shear stress () & velocity gradient (dv/dy) Units → Pa-s 96% fused silica glass soda-lime Pyrex silica 10 14 annealing range 10 10 Viscosity [Pa•s] T : soft enough 10 6 deform to deform or “work” 2 10 1 T(°C) 200 10 00 1800 1400 6 00 Glass Viscosity Modulation • Viscosity Decreases with • Increasing Temperature • The Addition of Impuritities

14. ANNEALING removes internal stress caused by uneven cooling TEMPERING puts SURFACE of glass part into Compression suppresses growth of cracks from SURFACE scratches. before cooling surface cooling further cooled cooler compression hot hot tension compression cooler Heat Treating Glass • Tempering Sequence • Result: Suppression of Surface Crack Growth

15. Ceramic Fabrication Methods-IIA PARTICULATE FORMING GLASS CEMENTATION FORMING pour slip absorb water drain pour slip “green into mold into mold A o mold “green into mold container ceramic” die holder ceramic” force ram billet A extrusion d die container • Milling and screening: desired particle size • Mixing particles & water: produces a “slip” • Form a "green" component • HydroPlastic Forming; • e.g.; Extrude into a Rod • Slip Casting Dry; then Fire At Hi-Temp

16. Clay is an Inexpensive Starting Material Adding water to clay allows material to shear easily along weak van der Waals bonds enables extrusion enables slip casting Shear charge neutral weak van der Waals bonding 4+ charge Si 3 + neutral Al - OH 2- O Shear The Nature of a Slip

17. Drying: Layer Size & Spacing Decrease wet slip partially dry “green” ceramic Si0 particle 2 (quartz) glass formed around the particle micrograph of porcelain m 70 m Drying and Firing • Firing: • T raised to 900-1400 °C • Vitrification: glass forms from clay and flows between SiO2 particles

18. Ceramic Fabrication Methods-IIB PARTICULATE FORMING GLASS CEMENTATION FORMING • Sintering: useful for both clay and non-clay compositions. • Sintering Procedure: • GRIND to produce ceramic and/or glass particles • INJECT into mold • PRESS at elevated Temp to reduce pore size. • Aluminum oxide powder: • Sintered at 1700C for 6 minutes (note Pores).

19. Produced in extremely large quantities. Portland cement: mix clay and lime bearing materials calcinate (heat to 1400C) Primary constituents: tri-calcium silicate di-calcium silicate Adding water To Portland Cement produces a paste which hardens hardening occurs due to hydration (chemical reactions with the water). Forming: done usually minutes after hydration begins Ceramic Fabrication Methods-III GLASS PARTICULATE CEMENTATION FORMING FORMING

20. noncrystalline: short range order Advanced Ceramics • Example = Metallic Glass • a.k.a.: “MetGlass” or “Liquid Metal” • Basic Processing Concept • Rapidly solidify from melt • i.e., Very Fast cooling rates • e.g from 1500 °F to Rm-Temp in 5 Seconds • Atoms have NO time to Order and become Crystalline

21. Liquid Metal Properties • Liquid Metals are Alloys of Ni, Zr, Ti, Cu, Be

22. Metallic Glass Mechanical Props • Metallic Glass has good mechanical properties because Metallic Glass has an amorphous structure and thus does NOT have slip Planes

23. SS vs MetGlass • MetGlass is Much STRONGER, but Also Much More FLEXIBLE • Good for “Springy” Structures • e.g; Golf Club Shafts

24. Summary – Ceramic Apps/Fab • Basic categories of ceramics: • Glasses • Clay products (whiteware) • Refractories (Tolerate Very High Temps) • Cements • Advanced Ceramics • Fabrication Techniques: • Glass Forming • Impurities affect forming Temperature

25. Summary – Ceramic Apps/Fab • Fabrication Techniques (cont): • Particulate forming • Needed if ductility is limited • Cementation (large volume, room Temperature process) • e.g.; Portland Cement • SuperRapid Cooling • e.g.; Metallic Glass

26. Summary – Ceramic Apps/Fab • Heat Treating Used To: • Alleviate residual stress from cooling, • Produce fracture resistant components by putting surface into compression • Tempering

27. WhiteBoard Work 1N • Problem 13.17 • SodaLime Glass (SLG) Loaded as Shown at Right • Find Using Fig 13.6 the Max-Temperature if the allowed extension is 1mm over the course of a week’s time • Ref. Next Slide SLG 100 mm 5 mm 1 N

28. Use Fig. 13.6 • The Viscosity Reln • Where • η Viscosity • σ Tensile Stress • ε  Tensile Strain 490 °C