By: Abu Bakar bin Aramjat Department of Ceramic Processing Technology Kolej Kemahiran Tinggi MARA Masjid tanah M e

1. GLASS PROCESSING ( DCP 5262 ) GLASS COMPOSITION & GLASS FAMILIES By: Abu Bakar bin Aramjat Department of Ceramic Processing Technology KolejKemahiranTinggi MARA Masjidtanah Melaka

2. GLASS COMPOSITION

3. GLASS COMPOSITION NETWORK/ GLASS FORMER SiO2 -. STABILISERS/ INTERMEDIATES Alkali & alkaline earth MODIFIERS Al2O3,

5. GLASS COMPOSITION • GLASS FORMER • -most inorganic glasses- based on the glass forming oxide silica-SiO2 • -form glassy structures • -also is known as network former • ( polyhedral oxide structures ) • SiO2 • B2O3 • P2O5 -.

6. GLASS COMPOSITION NETWORK MODIFIERS -Alkali & alkaline earth -these oxides do not form polyhedral networks. -their cations are incorporated within and modify the SiO4-4 network -breaks up the glass network -They lower viscosity so that it can be worked and formed easier. -.

7. GLASS COMPOSITION • ALKALI • -As fluxes, easy to melt glass at low temperature • -break up the glasses network • - easier to forming, lower viscosity • Na2O ( soda ash ) – important alkali in glass making • Lithia ( lithium carbonate ) – better flux than soda, better durability but expensive • Potassium (potash nitrate/ carbonate) – larger ionic size, less ion mobile, better electric insulator , flux effect below than soda -.

8. GLASS COMPOSITION • ALKALINE EARTHS • -As fluxes, BUT not so good as alkali • -Better in chemical durability, good dielectrik properties • CaO -lime ( limestone) – important alkali earth in glass making • MgO – magnesia ( dolomite ) -.

9. GLASS COMPOSITION • INTERMEDIATE/STABILISER • Oxides can’t form glass network by themselves but can join existing network. • Sometime act as network modifier , can also as network former if present amt less than alkalis • substitute for silicon and become part of and stabilize the network • Improves glass properties, decrease the tendency for crystallization, withstand high temp • Al2O3 , TiO2 -.

10. GLASS COMPOSITION -.

11. GLASS FAMILY/TYPES

12. Soda lime silicate glass • Common glass in the world • SiO2-CaO-Na2O • Also known as commercial glass or soda-lime glass, as soda ash is used in its manufacture. • Main constituent - sand. -.

13. Soda lime silicate glass • Sand by itself can be fused to produce glass but the temperature at which this can be achieved is about 1700oC. • Sand that has been processed into powder is called silica or silicon oxide. • Adding other minerals and chemicals to sand can considerably reduce the melting temperature -.

14. Soda lime silicate glass • The addition of sodium carbonate (Na2CO3), known as soda ash, to produce a mixture of 75% silica (SiO2) and 25% of sodium oxide (Na2O), will decrease softening point of glass to about 800oC.

15. Soda lime silicate glass • In order to give the glass stability, other chemicals like calcium oxide (CaO) and magnesium oxide (MgO) are needed. • These are obtained by adding limestone which results in a pure inert glass. • Add 1-4% MgO – prevent devitrification of glass • Add 0.5-1.5% Al2O3 – increase durability

16. Soda lime silicate glass • Commercial glass is normally colourless, allowing it to freely transmit light, which is what makes glass ideal for windows and many other uses. • Additional chemicals have to be added to produce different colours of glass such as green, blue or brown glass.

17. Soda lime silicate glass Most commercial glasses have roughly similar chemical compositions of: 70% - 74% SiO2 (silica) 12% - 16% Na2O (sodium oxide) 5% - 11% CaO (calcium oxide) 1% - 3% MgO (magnesium oxide) 1% - 3% Al2O3 (aluminium oxide) CULLET Flat glass is similar in composition to container glass except that it contains a higher proportion of magnesium oxide

18. Soda lime silicate glass Cullet – recycle glass - 85 – 90% of glass formulation Reducing Quarrying activity ENVIRONMENTAL BENEFIT saves energy reduces emissions.

19. Soda lime silicate glass • High electrical resistivity • Good dielectric properties • Good chemical durability • High thermal expansion • Good spectral transmission in visible region • Less expensive • Easy to fabricate

20. Soda lime silicate glass • Advantages • Easy to melt • Least expensive • Disadvantages • High thermal expansion • Thermal shock failure • Softness • Limited high temperature use

21. Soda lime silicate glass • Applications- Such as bottles and jars, flat glass for windows ,drinking glasses, containers, windscreen, decorative

22. Borosilicate glass • Boric oxide, B2O3 is often used as a flux in place of alkali oxide, where the resistance to thermal shock is needed • Its melting point is about 460oC • Together with SiO2 silica as network formers, they create glass that has low thermal expansion

23. Borosilicate glass • General composition : • SiO2 > 70-80% • B2O3 > 10-20% • Na2O/K2O > 10-15% • Al2O3 > 5-10% • SiO2 – B2O3 - Na2O - Al2O3

24. Borosilicate glass • High resistance to chemical attack • Good thermal shock resistance • Good chemical durability • Low thermal expansion • Very expensive • Applications: • Laboratory glassware, Pyrex, Households cooking utensils, chemical industry , fibres for textile and plastic reinforcement.

25. Borosilicate glass

26. Lead Glass • Alkaline –lead glass have a long working range (small change in viscosity with decrease in temp) • Used for fine handcraft, tableware and artware • Lead oxide is good flux which does not lower the elecrical resistivity as do the alkali oxide • Glass containing less than 24% PbO, is known simply as crystal glass.

27. Lead Glass • General composition of lead glass: • SiO2 > 50-65% • PbO > 20-74% • Na2O/K2O > 5-15% • SiO2 – PbO – Na2O

28. Lead Glass • The lead is locked into the chemical structure of the glass so there is no risk to human health. • Lead glass has • a high refractive index making it sparkle brightly and • a relatively soft surface so that it is easy to decorate by grinding, cutting and engraving which highlights the crystal's brilliance making it popular for glasses, decanters and other decorative objects.

29. Lead Glass • High degree of brilliance • High electrical resistivity • High fluidity and workability • Low thermal expansion • Expansive

30. Lead Glass • Glass with even higher lead oxide contents (typically 65%) may be used as radiation shielding because of the well-known ability of lead to absorb gamma rays and others harmful radiation • Fluorescent lamp envelopes • Television bulb • Optical glasses • Decorative glasses- crystal glass, chandeliers

31. Lead Glass

32. Aluminosilicate Glass • When alumina is added to an alkali silicate glass formulation, the glass becomes more viscous • In silicate glasses alumina is a network former and assumes a tetrahedral coordination • It diminishes the number of non-bridging oxygen, which increases the cohesiveness of glass structure • Commercial aluminosilicate glass can be heated to higher temperature without deformation

33. Aluminosilicate Glass • General composition of aluminosilicate glass: • SiO2 > 50-65% • Al2O3 > 15-30% • MgO/CaO > 10-15% • B2O3 > 5% • SiO2 – Al2O3 – Na2O - CaO

34. Aluminosilicate Glass • High resistance to chemical attack • High value elastic moduli • High temperature strength • Low thermal expansion • Expensive • Application: High efficiency lamp, glass insulator

35. Aluminosilicate Glass

36. Alkali-barium Silicate Glass • Without this type of glass watching TV would be very dangerous. • A television produces X-rays that must be absorbed; otherwise they could in the long run cause health problems. • The X-rays are absorbed by glass with minimum amounts of heavy oxides (lead, barium or strontium). • Lead glass is commonly used for the funnel and neck of the TV tube, while glass containing barium is used for the screen.

37. Technical Glass Technical is the term given to a range of glasses used in the electronics industry. Borate Glass • Without borate glass the computer revolution would not have been possible as it's vitally important in producing electrical components. • This type of glass, contains little or no silica and is used for soldering glass, metals or ceramics as it melts at the relatively low temperature of 450-550oC, well below that of normal glass, ceramics and many metals. • Glass of a slightly different composition is used for protecting silicon semi-conductor components against chemical attack and mechanical damage. • Known as passivation glass it is vital in microelectronics technology and the production of the silicon chips inside computers.

38. Technical Glass Chalcogenide glass • Similar semiconductor effects are also characteristic of a type of glass that can be made without the presence of oxygen. • Some of them have potential use as infrared transmitting materials and as switching devices in computer memories because their conductivity changes abruptly when particular threshold voltage values are exceeded.

39. Technical Glass Chalcogenide glass • Element: S, Se, Te, Ge, As, Sb • Properties: • Low melting temp • Photoconductivity • Good IR-transmission • Low Thermal expansion • Expensive

40. Technical Glass Halides Glass • ZrF4-NaF2-LaF3-AlF3 • Low melting temp • Low thermal expansion • Expensive • Example: Optical Glass.

41. Glass Fibre • Soda lime silicate and Alumino-borosilicate glass • Application: • building insulation and glass wool • Textiles • reinforced polymer composite to make protective helmets, boats, piping, car chassis, ropes, car exhausts • Optical fibre in endoscopes, telecomunication

42. Vitreous Silica • This glass is prepared by: • i. By heating silica or quartz crystal to a temp. above the melting point of silica 1725oC • ii. By vapour deposition process • SiCl4 is reacted with O2 at temp above 1500oC • A finely divided particulate vitreous silica is formed • This method can achieve high purity of vitreous silica -.

43. Vitreous Silica • 100% SiO2 • Most refractory glass • High chemical resistance to corrosion • Low electrical conductivity • Low thermal expansion • Good UV transparency • Very expensive • Application: astronomical mirror, space shuttle window, optical fiber -.

44. Glass Ceramic • Glass ceramics can be described as polycrystalline materials formed by controlled crystallization of glass • Discovered by Stookey (1950) – work at Corning Glass Works • Share many properties with both glasses and ceramic

45. Glass Ceramic • Have combination of amorphous phase and crystalline phases • Produce by so called “ controlled crystallization” • Consist of 30 -90% crystallinity • Glass ceramic contains 92% covalent bond & 8% ionic bond

46. Glass Ceramic • Properties • Opaque/ transparent • Brittle • Inert • Highly durable • Heat resistance

47. Glass Ceramic • Advantages • Inert • Does not corrode • Durable • High mechanical propeties • Low thermal expansion • Low heat conduction coefficient • Good thermal shock resistance

48. Glass Ceramic • Example of Glass Ceramic System • Lithium aluminosilicates ( Li2O-Al2O3-SiO2) • -LAS • 2. Magnesium aluminosilicates (MgO-Al2O3-SiO2) • MAS • 3. ZAS system – ZnO-Al2O3-nSiO2 • 4.Lithium DiSilicate • 5. Calcium Silicates • Nucleation agent : ZrO2 & TiO2

49. Glass Ceramic Applications Cooktop/Stovetop Cookwares/Casserolles Telescope mirrors High performance reflectors for digital projectors Insulator High performance tiles Machinable glass ceramic Fireplace wall/door

50. Glass Ceramic