Ceramics Materials

1. Ceramics Materials By: Engr. Rizwan Nasir September 15, 2009

2. Definition • Ceramic materials are inorganic, non-metallic materials and things made from them. They may be crystalline or partly crystalline. They are formed by the action of heat and subsequent cooling. • Clay was one of the earliest materials used to produce ceramics, but many different ceramic materials are now used in domestic, industrial and building products.

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 Adapted from Fig. 13.1 and discussion in Section 13.2-6, Callister 7e. household -sensors • Properties: -- Tg for glass is moderate, but large for other ceramics. -- Small toughness, ductility; large module. • Applications: -- High T, wear resistant • Fabrication -- some glasses can be easily formed -- other ceramics can not be formed or cast.

4. Processing of Ceramics Materials • Most traditional and technical ceramics product are manufactured by compacting powder or particles into shapes which are heated to high temperature. • The basic steps in the processing of ceramics are: • Material Preparation • Forming & Casting • Thermal treatment by drying

5. Material Preparation • Most ceramics products are made by the agglomeration of particles. • The raw materials for these products vary depending on the required properties of the finished ceramics parts. • The particles and other ingredients such as binders may be blended. Example • One type of high alumina (Al2O3) insulator, the particular raw materials are milled with H2O along with the wax binder to form a slurry which is subsequently spray dried to form small spherical pallets.

6. Forming & Casting • Ceramics products made by agglomeration, particles may be formed by the variety of methods in a dry, plastic or liquid form. • Forming is subdivided in: • Dry pressing • Iso static Pressing • Hot pressing

7. Dry Pressing Dry pressing may be defined as The simultaneous uniaxial compacting and shaping of a granular powder along with small amount of H2O and binder in a dye. • Dry pressing ceramic is the most economic process for large production runs, and is suitable for both simple and complex geometries. • Depressions and holes are normally only designed in the pressing direction.

9. Isostatic Pressing • Isostatic pressing enables to produce various types of materials from powder compacts by reducing the porosity of powder mixture. • The powder mixture is compacted encapsulated using isostatic pressure, it means by using pressure equally from all directions. • In this process the ceramics powder is loaded into a flexible air tight container.

10. Cold Isostatic Press (CIP) • This forming method involves pressing dried and granulated raw materials into a shape close to that of the finished product. • The granulated raw materials are poured into a rubber mold. • The mold is then put in a high-pressure container, where hydraulic pressure is applied evenly from all directions (isostatic pressing) in order to provide uniform, highly dense compaction. • This method is ideal for forming products with large dimensions.

11. Hot Isostatic Pressing (HIP), • Hot Isostatic Pressing (HIP), the simultaneous application of heat and high pressure, has become a standard production process in many industries. In the HIP unit a high temperature furnace is enclosed in a pressure vessel. Work pieces are heated and an inert gas, generally argon, applies uniform pressure. The temperature, pressure and process time are all controlled to achieve the optimum material properties.

12. Slip Casting • Slip casting is one of the simplest methods of reproducing ceramic objects. • It has the advantage of permitting the making of a large number of exact replicas of an original model-such as identical sets of plates, ash trays, vases, statuettes, bowls, and others-with a minimum of effort. • With slip casting it is possible to cast duplicates of most models which are made by the plastic method.

13. --Slip casting: drain pour slip pour slip “green absorb water mold Adapted from Fig. 13.12, Callister 7e. (Fig. 13.12 is from W.D. Kingery, Introduction to Ceramics, John Wiley and Sons, Inc., 1960.) into mold into mold into mold ceramic” “green ceramic” solid component hollow component Process of Slip Casting The main steps in slip casting are: • Preparation of powdered ceramics material & a liquid clay and water • Pouring the slip into a pores which made of plaster of paris and allowing liquid portion to absorb by the module. • When a sufficient wall thickness has been formed, the casting process is interrupted and the excess slip is poured out of cavity. • The material in the mould is allowed to dry to provide adequate strength for handling and removal of the part from the mould. • Finally the cast part is fired to attain the required properties.

14. Ceramics Compound and their Melting Points

16. Glass

17. Definition • A glass can be defined as an inorganic product which has cooled to rigid structure without crystallization. • Glass is hard material normally fragile and transparent common in our life. It is composed of mainly: • Sand • Alkali

18. Ingredients TO Obtain Glass • There are following main ingredients used in he manufacturing of glass: • Sand • Soda Ash • Limestone

19. Natural Resources • Silica sand 72% • Soda Ash 17% • Lime 5% 17% 5% 72% 6%

20. Silica Sand

21. Silica Sand • Three of most common rock forming minerals on earth • Chemically named: quartz sand / rock crystal • Properties: • Extremely heat durable • Chemical stack resistance

22. Formation of Silica Sand • Naturally: • Mechanical & chemical weathering of quartz-bearing igneous & metamorphic rocks • Chemically weathering: • Less stable minerals • break down to become silica sand • More stable minerals • release to environment • Carry by wind / wave • Sort by wave & stream action to form pure silica sand

23. Location & Integration of Silica Sand • It is found below thin layers of overburden & soil as unconsolidated deposits • It is abundant resource on earth crusts (44%) and occur throughout the world. • Best known place in U.S.: • NE of town of Hudson Bay along the Red Deer River

24. Silica sand resources is abundant on the world. Its extraction is limited by geographic distribution quality requirements for some uses environmental restrictions Extraction of theses resources is dependent on whether it is economic and are controlled by the location of population centers World resources of Silica Sand Fig. 1 http://minerals.er.usgs.gov/minerals/pubs/commodity/silica/780397.pdf

25. Purposes for the Utilize of Silica Sand • History: • Glass making & metallurgical activities few thousands years BC ago • Key raw material in ceramics, foundry & glass industrial revolution • Today: • Glass making, foundry casting, ceramics, filtration, specialist building applications, leisure ( e.g. golf course), filters in numerous products, plastics, the manufacture of chemicals, metal & refractory, as addictives in horticultural & agricultural products & simulating oil production

26. Purposes for the Utilize of Silica Sand Cont’ • Important for today’s information technology: • Raw material for silicon chips • Plastics of computer mouses

27. Soda Ash

28. Soda Ash • Anhydrous sodium carbonate • Texture: soft • Color: grayish & white • Appearance: lump / powder in nature

29. Location & Integration of Soda Ash • Integrated as sodium –rich waters (brines) / extensive beds of trona (tri sodium hydrogendicarbonate di hydrate); Na3H(CO3)2·2H2O ) • Large soda ash deposits: • U.S, Mexico, Canada, Kenya, Botswana, Uganda, Peru, Germany, India, Egypt, S. Africa & Turkey • World’s largest trona deposit: • Green River Basin of Wyoming • estimate to have 47 billion tons of soda ash

30. Purposes for the Utilize ofSoda Ash • History: • Early Egypt: make glass & soap • Early Roman: make glass, bread & pharmaceuticals (medicine) purpose to cure choric & skin rashes

31. Purposes for the Utilize ofSoda Ash Cont’ • Glass manufacture (49%) • Chemical production (27%) • Mineral processing in mining • Pulp & Paper manufacturing • Sodium compounds manufacturing • Soap & detergents (11%) • Water treatment (2%) • Textile processing • Glass fiber manufacture • Cleaning preparations • Petroleum refining • Metallurgical refining • Removal of sulfur from smokestack emissions (3%) • Distributors (5%) • Metal refining Important merchandise for U.S.:

32. Lime

33. Location & Integration of Lime • Underneath the topsoil , ach, & siltstone • Associated in: • Limestone • Marine organisms on seabed e.g. seashells

34. Purposes for the Utilize ofLime Historical Use: • Ancient Egyptian civilization used lime to make plaster and mortar. Nowadays: • Use extensively for: glass making, the pulp & paper industry & steel mills • Other uses: municipal & industrial water / wastewater treatment, as an addictive for road stabilization & construction projects • In U.S., more than 90 % of lime production is for chemical and industrial uses

35. Today’s Glass Manufacturing Process: • Silica sand, limestone, soda ash and cullet (recycled glass or broken glass) are keep dry and cool in a batcher house in silos or compartments • Mixing and weighting into proper proportion • Send to furnaces in hoppers • operated by natural gas • heat the mixture at 1300-1600 degrees Celsius into soften or molten state Fig.12 www.glassforever.co.uk/howisglassmade/

36. 4. Molding --- molten glass flows to forming machine to mold into desire shapes 5. Annealing lehrs --- reheating the glass in an oven • to ensure even cooling of glass for strengthening of the products 6. Cooling process --- Cool for 30 min to an hour for safe to handle. 7. Glass products are then decorated, inspected again and finally packaged and shipped to our customers. glass furnace cooling systems

37. Properties Solid & Hard Disorder & Amorphous Structure Fragile Transparent Glass does not crude Uses Architectural Applications Illumination Electrical Transmission Instruments for scientific research Optical instruments Domestic tools Reaction vessel (due to corrosion resistant) Properties & Uses

38. Types of Glass There are the following types • Fused silica glass • 96% silica glass • Soda lime glass • Lead silicate glass • High lead glass • Boron silicate glass • Alumina borosilicate glass • Low alkali glass • Alumina silica glass • Glass ceramics

39. Fused Silica Glass • Fused silica is a noncrystalline (glass) form of silicon dioxide. It contains 99.5% silica Typical of glasses, it lacks long range order in its atomic structure. It’s highly cross linked three dimensional structure gives rise to it’s high use temperature and low thermal expansion coefficient. Key Properties • Near zero thermal expansion • Exceptionally good thermal shock resistance • Very good chemical inertness • Can be lapped and polished to fine finishes • Good UV transparency. Typical Uses • It is an ideal glass for space for space technology. • It is used for optical system in spectrometric devices. • It is difficult to process and is therefore very expansive.

40. Soda Lime glass • It is most commonly produced glass which accounts for 90% of all the glass produced in the world. In this glass component are: • 71 – 73% SiO2 • 12 – 14% Na2O • 10 – 12% CaO The Na2O & CaO decrease the softening point of this glass from 1600oC to 730oC So that soda lime glass is easier to form. An addition of 1 – 4% MgO is added to Soda lime glass to prevent cracks. In addition of 0.5 – 1.5% Al2O3 is used to Increase the durability

41. Uses • Soda lime glass is used for flat glass, containers, lightening products. • It is used where chemical durability and heat resistant are not needed.