MATERIALS IN PRACTICE

Transcription

1 MATERIALS IN PRACTICE Office Hours: Friday, 16:30-17:30 Phone: Metallurgical and Materials Engineering Department

2 OBJECTIVE To provide a basic understanding of glass materials. To understand processing, properties, characterisation and design of these materials.

3 REFERENCES Shackelford, James F., Doremus, Robert H. (Eds.), Ceramic and Glass Materials Structure, Properties and Processing, Springer, Wolfram Holand, George H. Beall, Glass Ceramic Technology, John Wiley & Sons, Glass Science, R. H. Doremus, Wiley, Adalbert Feltz, Amorphous Inorganic Materials and Glasses, Wiley, D. W. Richerson, "Modern Ceramic Engineering," Second Edition, Marcel Dekker Inc., W.D. Kingery, H.K. Bowen, and D.R. Uhlmann, Introduction To Ceramics, John Wiley and Sons, 1976.

4 ISSUES TO ADDRESS What is glass? Classification of glasses Processing and properties of glasses Typical applications of glasses

5 GLASSES GLASSES Ceramic Materials

6 What Do You Know About Glasses? DEFINITION What is glass? PROPERTIES What are the general properties of glassses? APPLICATIONS What are the main application areas of glassses?

7 Well Known Glass Products Classic Wolfard Oil Lamp Heat resistant glassware (microwave safe) Heat resistant glass lid Tempered Glass Cutting Board

8 Well Known Glass Products Tempered glass table Glass sink cabinets in the bathroom ucts.php Laminated Windscreen Glass Heat resistant glass door

9 Well Known Glass Products Glass Bathtub Glass splashbacks Hirom Glass Violin is a product of Hario Glass Co. Ltd., Japan. And also, The world s first hand made glass violin. Superdurable tempered glass Wall-to-wall glass windows

10 Well Known Glass Products

11 Consumption of Glass Glass Consumers Glass package, 43 % Sheet glass, 30 % Housekeeping, 12 % Electrotechnical needs, 10 % Plant and cunduits, 5 % Three largest consumers Glass packaging, domestic commodities and construction industry

12 GLASSES Four of the major technological achievements in glass which have had the most profound impact on mankind. Glass window which enables sunlight to come into dwelling unit Lenses opthamics for improved vision, microscope, telescope optics Light bulb envelope - lighting Semiconducting glasses for computer memory, solar cell, photocopiers

13 Advantages and Limitations of Glasses Advantages Inert Does not corrode Durable Optical transparency Many forming method Many composition Cheap Disadvantages Brittle Breakable Heavy

14 History of Glass The word glass is derived from a late-latin term glaesum, used to refer to a lustrous a transparent material. Another word often used to refer to glassy substances is vitreous, originating from the Latin word vitrum. Luster or shine and in particular its durability when exposed to the elements of nature, were probably the most significant properties of glass recognised by early civilisations.

15 The Beginnings of Glass Technology The earliest written records of glass making are some famous clay tablets, dating from around 650 BC, from the library of Assur-bani-pal, but these are incompletely understood because we have no dictionary to explain the technical terms. Many centuries passed before written accounts of glass making contained any useful insight besides recipes to be followed by rote. The earliest development in glass making of which we have a reasonably documented description seems to be the invention of glass of lead by Ravenscroft around

16 GLASSES In 1960, glass production is divided into three large groups Glass for domestic and industrial use Glasses Architectural glass Art glass

17 What is Glass? A glass is a solid that possesses no long-range atomic order and which undergoes the glass transformation from solid to supercooled liquid on heating. Crystalline materials have a definite structure, whereas amorphous ones do not, and therefore only rather general statements can be made about a material which, when hot, is ductile but when cold is brittle, and fractures if there is a sudden change of temperature. Amorphous solids No crystal structure No longrange order Resemble frozen liquids No melting point, a glass transition temperature

18 What is Glass? Glass is a very brittle material Glass is a linear elastic and isotropic material with no plastic behavior at normal temperatures, which can explain its brittle fracture. It follows Hooke s law.

19 AMORPHOUS versus CRYSTALLINE Glass has amorphous structure Crystalline materials have some periodic crystal structure that results in long term order

20 Glass Properties General properties of glasses High hardness / brittle Low density compared to high strength Low thermal expansion coefficient Low heat / electrical conductivity High melting point Good chemical resistance / chemically inert Wide range of optical transmission Transparent Translucent Opaque

21 Glass from Nature magma fulgurite obsidian

22 History of Glass : Obsidian : Discovery by chance of the glass melting (Persia Mesopotamy)

23 History of Glass -4000: Jewel in molted glass -(Phoenicia)

24 History of Glass -1500: Vases and vessels (Egypt)

25 History of Glass - 200: Glass blown with a pipe (Syria)

26 History of Glass -100: 1 st glazing : Casted glass on table (Rome) 76: Pompei From 2 nd to 12 th : regression of the glass

27 History of Glass Crown method (6 th century)

28 History of Glass Cylinder method (12 th century)

29 Processing of Glass Starting ceramic powders Final product Batching and mixing of raw materials Homogenisation Batch melting Fining Glass is prepared by cooling from a liquid state without crystallization

30 ORDINARY GLASS FABRICATION SAND SODA LIME OTHER GLASS Percentage of Ingredients in Glass

31 Composition of Some Typical Glasses Typical composition (wt %) of some of the common commercial glasses

32 Types of Glasses The main types of glass are: Commercial glass also known as soda-limesilicate glass Lead glass Borosilicate glass Glass fibre Special glasses Layered glass Tempered glass

33 Float Glass Annealed glass Annealed ( ordinary ) glass is the end product of the float glass process. It is carefully cooled through the range of temperatures where the glass solidifies so that no residual stresses develop. Float glass is made using a bath of molten tin, where molten glass is floated along the surface. The perfectly flat surface of the tin is transferred to the glass. Advantages Low cost Disadvantages Breaks in sharp pieces Not as strong as tempered glass Size limitations

34 Float Glass Fabrication Sand, soda ash, limestone, salt-cake, dolomite are melted at 1600 C Poured into a bath of molten tin at 1100 C Controlled atmosphere Glass settles and is pulled out at 600 C and annealed Furnace Molten tin Float bath Lehr Washed, cut & stored

35 Float Glass Float Glass Used For Mirrors In Building

36 LEAD GLASSES LEAD GLASSES are used for high refractive index, easier working and greater density for lamp envelopes, seals, optical glass CRYSTAL GLASS for art and tableware

37 LEAD GLASSES Leaded Stained Glass Windows This type of glass has been mixed with lead-rich materials while molten; lead replaces the calcium content of a typical glass. Lead glass has a long history. The earliest known example with lead oxide additives is a blue glass fragment from Nippur dated to 1400 BC. Leaded stained glass was first used in medieval Europe as a base for colored glass. This glass was used in mosaic tiles, enamels, stained glass painting, and to imitate precious stones. Lead oxide was used to create enamel for vessels and windows because of its lower working temperature. By the 17th century George Ravenscroft produced the first clear lead glass on a large sale. Taking advantage of his merchant class status, Ravenscroft was able to revolutionize the glass trade and shifted England into the leader as a leaded glass innovator. Scotland, especially Glasgow, became the world center for creating leaded glass windows and glassware. Lead glass in your home s windows will not cause lead poisoning. However, it is still not safe to lick, chew, or eat your leaded glass windows. As long as you adhere to those rules, you will not risk lead poisoning.

38 BOROSILICATE GLASSES BOROSILICATE GLASSES lower thermal expansion better thermal shock resistance, improved chemical durability, for such applications as automobile head-lamps, cooking wares and laboratory apparatus

39 BOROSILICATE GLASSES Borosilicate pyrex type colored tubing for glassblowing Pyrex labware is made of borosilicate glass Borosilicate glass erlenmeyer flasks Borosilicates headlights on cars and Pyrex (heat resistant glass) Pressure resistant circular panes for sight glasses made of thermally toughened borosilicate glass, which are designed to withstand a continuous onesided fluid pressure at temperature up to 280 C

40 History of the glass Laminated glass: 1909 Tempered glass: 1929 (automotive)

41 Laminated Glass 2 sheets of glass are bonded with a thin film of plastic such as polyvinyl butyrate under pressure at a temperature of about 100 C Laminated glass is a kind of safety glass which is combined from one or more layers of PVB through heating and pressing processes by autoclave. The sandwiched plastic bonds well to the 2 glass surfaces and helps absorb energy in impacts, stops glass shattering and disintegrating if stressed to failure so that it often remains secure and weatherproof. This provides a high degree of resistance to injury from flying glass in case of impact.

42 Laminated Glass Laminated glass absorbs energy of the impact Ordinary window glass is brittle and breaks into long sharp pieces Safety Will not shatter Holds up against hurricanes cyclones earthquakes

43 Laminated Glass Laminated glass is widely used for bullet proof burglar-proof showcase counter aquarium skylight long corridor sidelite, etc. Glass staircase Laminated Windscreen Glass If the laminated glass is made from ordinary float glass, it is still workable (cutting and drilling is possible) and the PVB helps the fractured glass to stay put inside the construction.

44 Laminated Glass BULLETPROOF GLASS Bulletproof glass is made of laminated glasses and films which have special shielding capability towards bullets. The different levels of bullet proof glasses are able to shield the bullets from penetration and prevent the broken parts from injuring people. They are widely applied in bank, counters of jewelry and gold shops, cash trucks and other regions requiring special safety prevention millimetre glass/plastic laminate with a polycarbonate coating on the inside to prevent flying splinters. The 22-millimetre glass protects against: Blunt instruments.44 Magnum with full-jacket flat-nose bullets.357 Magnum with coned bullets 9-millimetre Luger with round-nose bullets

45 Tempered Glass Shatter pattern of tempered glass Tempered glass also know as toughened glass is made by quickly cooling the annealed glass when it is heated near compression is formed over the glass surface whiletensile formed inside the glass plate. Crazed fracture pattern on left in tempered glass on an elevator wall. Fracture origin is shown above. Tempered glass is made by heating annealed glass to approximately 700 C then cooling the outer surfaces rapidly. This process makes the glass very strong and shock resistant thus more durable.

46 Tempered Glass Usage Range of Tempered Glass: Construction curtain wall Glass doors & windows Support bar of staircases & escalators Different types of the glass artdecorations Location of near the intense heat the impact severed by the hot cold.

47 General Characteristics of Glasses Short range atomic order but no long-range order Structure is isotropic, so the properties are uniform in all directions Typically good electrical and thermal insulators Soften before melting, so they can be formed easily by various forming techniques

48 THE END Thanks for your kind attention

49 Any Questions