A member of NSG Group,2,Application of Inorganic Chemistry in Industry,Flat Glass and Coatings On Glass Dr Troy Manning Advanced Technologist, On-line Coatings Pilkington European Technical Centre Hall Lane Lathom UK ,3,Outline,Overview of Flat Glass industry and NSG/Pilkington Flat Glass manufacture Float Glass Process Coating technology within the glass industry Chemical Vapour Deposition Examples of on line coating applications Low Emissivity/Solar Control Self Cleaning Summary Suggested Reading,4,Global Flat Glass Market,Global Market 37 million tonnes (4.4 billion sq. m) Building Products 33 m tonnes - Automotive 4m tonnes Of which 24 million = high quality float glass 3 million = sheet 2 million = rolled 8 million = lower quality float (mostly China) Global Value At primary manufacture level 15 billion At processed level 50 billion,5,NSG and Pilkington combined,A global glass leader the pure play in Flat Glass Combined annual sales c. 4 billion Equal to Asahi Glass in scale, most profitable in Flat Glass Ownership/interests in 46 float lines 6.4 million tonnes annual output Widened Automotive customer base 36,000 employees worldwide Manufacturing operations in 26 countries Sales in 130+ countries,6,Manufacture of Flat Glass,Four main methods Plate Glass (1688) molten glass poured on to a flat bed, spread, cooled and polished Sheet Glass (1905) continuous sheet of glass drawn from tank of molten glass Rolled Glass (1920) molten glass poured onto to two rollers to achieve an even thickness, making polishing easier. Used to make patterned and wired glass. Float Glass (1959) molten glass poured onto bed of molten tin and drawn off in continuous ribbon. Gives high quality flat glass with even thickness and fire polish finish. 320 float-glass lines worldwide,7,Melting furnace,Float bath,Cooling lehr,Continuos ribbon of glass,Cross cutters,Large plate lift-off devices,Small plate lift-off devices,Raw material feed,The Float-Glass Process,Operates non-stop for 10-15 years 6000 km/year 0.4 mm-25 mm thick, up to 3 m wide,8,The Float Glass Process,9,Raw materials,10,Melting Furnace,11,Float Bath,12,Float Glass Plant,13,The Float-Glass Process,Fine-grained ingredients, closely controlled for quality, are mixed to make batch, which flows as a blanket on to molten glass at 1500 C in the melter. The furnace contains 2000 tonnes of molten glass.,After about 50 hours, glass from the melter flows gently over a refractory spout on to the mirror-like surface of molten tin, starting at 1100C and leaving the float bath as a solid ribbon at 600C.,Despite the tranquillity with which float glass is formed, considerable stresses are developed in the ribbon as it cools.,14,Raw Materials,Oxide % in glass Raw material source SiO272.2Sand Na2O13.4Soda Ash (Na2CO3) CaO8.4Limestone (CaCO3) MgO4.0Dolomite (MgCO3.CaCO3) Al2O31.0Impurity in sand, Feldspar or Calumite Fe2O30.11Impurity in sand or Rouge (Fe2O3) SO30.20Sodium sulphate C0.00Anthracite,15,Raw materials,SiO2Very durable, BUT high melting point (1700C)! + Na2OMelts at a lower temperature, BUT dissolves in water! + CaOMore durable, BUT will not form in bath without crystallisation + MgOGlass stays as a super-cooled liquid in bath, no crystallisation + Al2O3Adds durability + Fe2O3Adds required level of green colour for customer,16,Chemistry of Glass,Important glassmaking chemistry: basic reactions Na2CO3 + SiO2 1500C Na2SiO3 + CO2 Na2SiO3 + x SiO2 Na2SO4 (Na2O)(SiO2)(x+1),Digestion,17,Composition of Glass,18,Structure of Glass,Random network of SiO4- tetrahedral units. Na-O enter Si-O network according to valency Network Formers Ca and Mg Network Modifiers make structure more complex to prevent crystallisation,19,Body-tinted Glass,20,CIE L a* b* colour space,21,CIE L a* b* colour space,22,Functions of a Window,Light in homes, offices Light out shops, museum displays Heat in heating dominated climates Heat out cooling dominated climates Can change properties of glass by applying coatings to the surface,23,Making a window functional - coatings,A wide variety of coating technologies are utilised by the glass industry Spray Pyrolysis Powder Spray Chemical Vapour Deposition Sputter Coating Thermal Evaporation Coatings Sol Gel Coatings These are applied On Line i.e. as the glass is produced on the float line Off Line i.e. coating not necessarily produced at the same location,24,Variations of CVD,Atmospheric Pressure APCVD Low Pressure - LPCVD Aerosol Assisted - AACVD Metalorganic MOCVD Combustion/Flame CCVD Hot Wire/Filament HWCVD/HFCVD Plasma Enhanced - PECVD Laser Assisted LACVD Microwave Assisted MWCVD Atomic Layer Deposition ALD,25,Chemical Vapour Deposition,26,Chemical Vapour Deposition,Main gas flow region,Gas Phase Reactions,Surface Diffusion,Desorption of Film Precursor,By Products,Diffusion to surface,27,Chemical Vapour Deposition,Animation kindly supplied by Dr. Warren Cross, University of Nottingham,28,CVD processes and parameters,29