1、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 manufactur
2、e 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
3、 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 leade
4、r 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 Sa
5、les 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
6、 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 f
7、urnace,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,Me
8、lting 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,
9、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
10、,Raw Materials,Oxide % in glass Raw material sourceSiO2 72.2 Sand Na2O 13.4 Soda Ash (Na2CO3) CaO 8.4 Limestone (CaCO3) MgO 4.0 Dolomite (MgCO3.CaCO3) Al2O3 1.0 Impurity in sand, Feldspar or Calumite Fe2O3 0.11 Impurity in sand or Rouge (Fe2O3) SO3 0.20 Sodium sulphate C 0.00 Anthracite,15,Raw mater
11、ials,SiO2 Very durable, BUT high melting point (1700C)!+ Na2O Melts at a lower temperature, BUT dissolves in water!+ CaO More durable, BUT will not form in bath without crystallisation+ MgO Glass stays as a super-cooled liquid in bath, no crystallisation+ Al2O3 Adds durability+ Fe2O3 Adds required l
12、evel of green colour for customer,16,Chemistry of Glass,Important glassmaking chemistry: basic reactionsNa2CO3 + SiO2 1500C Na2SiO3 + CO2Na2SiO3 + 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 networ
13、k 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 dom
14、inated climates Heat out cooling dominated climatesCan 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 Coa
15、ting 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
16、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 ofFilm Precurs
17、or,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,CVD Precursor Properties,Volatile gas, liquid, low melting point solid, sublimable solid Pure Stable under transport React/Deco
18、mpose cleanly to give desired coating minimise contaminants Can be single source or dual/multi-source,30,CVD Precursors,Single Source pyrolysis (thermal decomposition) e.g Ti(OC2H5)4 TiO2 + 4C2H4 + 2H2O (400 C) Oxidation e.g SiH4(g) + O2(g) SiO2(s) + 2H2(g) Reduction e.g. WF6(g) + 3H2(g) W(s) + 6HF(
19、g) Dual source e.g. TiCl4(g) + 4EtOH(g) TiO2(s) + 4HCl(g) + 2EtOEt(g),31,Dual Source and Single Source Precursors,32,Transport of Precursors,Bubbler for liquids and low melting solids,Direct Liquid Injection syringe and syringe driver for liquids and solutionsSublimation for solids hot gas passed ov
20、er heated precursor Aerosol of precursor solutions,33,Effect of Temperature on Growth Rate,Independent of temperature,34,Flow conditions,Laminar Flow regime,Turbulent Flow Regime,35,Reynolds Number,Dimensionless number describing flow conditions,r = Mass density related to concn and partial pressure
21、 u = average velocity = viscosity L = relevant length, related to reactor dimensions,If Re 1000 fully turbulent flow Reality is between the two extremes,36,Dimensionless Numbers,Reduces the number of parameters that describe a system Makes it easier to determine relationships experimentally For exam
22、ple: Drag Force on a SphereVariables: Force = f (velocity, diameter, viscosity, density) Can be reduced to 2 “dimensionless groups”:Drag coefficient (CD) and Reynolds number (Re),37,Dimensionless Numbers,Laminar flow regime,Turbulent flow regime,Experimental values of CD for spheres in fluid flows a
23、t various Re,38,Boundary Layer gas velocity,Frictional forces against reactor walls decrease gas velocity,The boundary layer thickness can be estimated from:,39,Boundary Layer - temperature,Contact with hot surfaces increases temperature,40,Boundary Layer precursor concentration,Depletion of precurs
24、or decreases gas phase concentration,41,Nucleation and Growth,Van der Waals type adsorption of precursor to substrate,Precursors then diffuse across surface,Precursors diffuse across boundary layer to surface,And can be desorbed back into main gas flow,Or can find low energy binding sites to coalesc
25、e into film,Main Gas Flow,42,Nucleation and Growth,43,Growth Mechanisms,(b) Frank - van der Merwe,Layer growth,(c) Stranski - Kastanov,Mixed layered and island,growth,(a) Volmer - Weber,Island growth,44,Thin Film Analysis,Many techniques are used to characterise thin films Examples include XRD cryst
26、allinity, phase XRR layer thickness, layer roughness SEM/EDX/WDX morphology, thickness, composition Raman phase, bonding FTIR phase, bonding XPS composition, depth profiling, doping SIMS composition, depth profiling, doping AFM roughness, surface morphology TEM crystalline structure, crystal defects
27、 Analysis of functional properties,45,CVD on Glass,For on-line coating of glass we require: High growth rates required thickness in 2 s Stable chemistry uniform coatings for continuous operation for many days Good adhesion to glass High efficiency reduce costs,46,APCVD Strengths and Weaknesses,47,On
28、-Line Coating Positions,Load raw materials,48,Laminar Flow CVD Coater,49,APCVD Applications on Glass,Coating technology allows us to add functionality to glass Coating technology is today used for a variety of products Low Emissivity coatings to reduce heating bills Solar Control coatings to reduce
29、solar heat gain Technical products e.g. TCOs for LCD displays, solar cells Anti-Reflective Products Hydrophobic Coatings Self Cleaning Coatings Smart Coatings e.g. electrochromics, thermochromics, photochromics,50,Low-Emissivity Coatings,Designed to reduce heating bills,In a double glazed unit, a lo
30、w-emissivity coating on the inner pane blocks radiative heat trying to escape into the cavity,51,Emissivity,Emissivity is the ratio of radiation emitted by a blackbody or a surface to the theoretical radiation predicted by Plancks law. Surface emissivity is generally measured indirectly by assuming
31、that e = 1 - reflectivity, usually at a specified wavelength,52,Solar Spectrum,We have to distinguish between : what comes from the outside to the inside solar spectrum what goes from the inside to the outside - heat,Visible light,Infra-Red,UV,53,Outside to Inside,Optimal curve for solar control - n
32、o UV - all visible light pass - no IR,Optimal curve for low-e - no UV - all visible light pass - all IR pass,54,Inside to Outside No Glazing,55,Inside to Outside Low-e Coated Glass,Low emissivity coated products limit the black body radiation i.e. the energy losses through the window:K-Glass e=0.15,
33、56,Transparent Conducting Oxides,Doped metal oxides displaying n-type conductivity F- substitutes for O2- in the SnO2 lattice releasing an electron into the conduction band i.e. Sn4+O2-2-xF-xe-x Close to metallic conductivity (15 W/) can be achieved but with high optical transmittance (band gap 4 eV
34、),C. G. Granqvist, Adv. Mater., 2003, 15, 1789-1803,57,CVD of SnO2:F,SnCl4 + H2O + HF SnO2:F + HCl (1.5 at% F) Much gas phase reaction Gases introduced separately in turbulent flow regime Very high growth rates 100 nm/s possible Low precursor efficiency 10%,SiCxOy (70 nm),SnO2:F (350 nm),Glass,SiH4
35、+ C2H4 + CO2 SiCxOy + H2O + other by-products Used as colour suppression and barrier layer,58,Low Emissivity Coating,Generally based on SnO2:F (Transparent Conductive Oxide) SiCO under layer used as colour suppressant,59,Low-E and Solar Control Coatings,60,Self-Cleaning Glass,Two mechanisms: Super h
36、ydrophilicity Photocatalytic degradation of organic matter.TiO2 coating,61,Superhydrophilicity,Oxygen vacancies,O,H,O,O,O,O,H,H,H,2,O,(,O,H,-,H,+,),Water droplets,Uniform water film,UV illumination time,Contact angle,o,o,o,o,o,o,o,dark,UV,62,Photocatalytic Activity,Ultra band gap irradiation of TiO2
37、 Generation of electron hole in valence band Hole migrates to the surface and results in oxidation of organic material,63,Semi-conductor Photocatalysis,A. Mills, S Le Hunte, J. Photochem. Photobiol A, 1997, 108, 1-35.,64,CVD of ActivTM,SiO2 (30 nm),TiO2 (17 nm),Glass,SiH4 + O2 + C2H4 SiO2 + by-produ
38、cts Used as barrier layer to prevent diffusion of Na ions into TiO2 layer,TiCl4 + EtOAc TiO2 + HCl + organic by-products,Laminar Flow regime Reasonable growth rates and precursor efficiency,65,ActivTM,66,ActivTM,67,ActivTM,68,Superhydrophilicity,15 mins UV Exposure,30 mins UV Exposure,45 mins UV Exp
39、osure,Before UV Exposure,69,Photocatalytic Effect,UV-Absorption O2 - OH*,Organic Soil,H2O + CO2,Glass,Barrier Layer,TiO2 - Layer,70,Photocatalytic Effect,The photoactivity of the coating can be measured by monitoring the decomposition of a standard contaminant A thin film of stearic acid (n-octadeca
40、noic acid, 200) is applied from a methanol solution onto the coating Stearic acid used as a typical organic contaminantFTIR (Fourier transform infra-red spectroscopy) used to detect C-H stretch of stearic acid C-H absorption intensity measured after varying UV exposure,71,Stearic Acid Decomposition,
41、C-H Absorption Zero UV exposure,C-H Absorption 60 mins UV exposure,UV 0.77W/m2 340nm,72,Pilkington ActivTM,73,Summary,Scale of the Global Flat Glass Industry Manufacturing Flat Glass Float Glass Process Coating Glass Chemical Vapour Deposition Examples of commercial glazing coatings prepared by CVD,
42、74,Recommended Reading,D.W. Sheel and M.E. Pemble Atmospheric Pressure CVD Coatings on Glass, ICCG4 2002 http:/www.cvdtechnologies.co.uk/CVD%20on%20Glass.pdf M.L. Hitchman, K.F. Jensen Chemical Vapor Deposition Academic Press, 1993 W.S. Rees, CVD of Non-metals, VCH, Weinheim, 1996 M. Ohring The Materials Science of Thin Films, Academic Press, 2001 ,First in Glass,
