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ICF Technical meeting, Sienna November 05th , 2007

New High Zirconia fused cast material for high quality glass without low temperature oxygen blistering. ICF Technical meeting, Sienna November 05th , 2007. New High Zirconia fused cast material for high quality Glass without low temperature oxygen blistering. Topics of the presentation.

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ICF Technical meeting, Sienna November 05th , 2007

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  1. New High Zirconia fused cast material for high quality glass without low temperature oxygen blistering ICF Technical meeting, Sienna November 05th , 2007

  2. New High Zirconia fused cast material for high quality Glass without low temperature oxygen blistering Topics of the presentation • Main interest of HZFC material in high quality glass • Low temperature oxygen blistering phenomenon • Hypothesis of mechanism with HZFC • How to prevent oxygen blistering • Properties of new HZFC • Influence of crystal glass composition evolution regarding AZS and HZFC materials

  3. 1 Interest of HZFC in quality glass

  4. Al2O3 SiO2 Zirconia Glassy phase 100 µm ZrO2 High Zirconia Fused Cast Microstructure Typical composition microprobe mapping Al2O3: 0.4 - 2 % ZrO2 > 90 % SiO2: 3 - 7 % Na2O: 0 – 0.4 % B2O3: 0 – 1 % Na2O

  5. Zirconia Glassy phase Corundum / Zirconia eutectic Fused Cast AZS Microstructure Typical composition microprobe mapping Al2O3: 46 % ZrO2: 41% SiO2: 12 % Na2O: 1% Al2O3 ZrO2 Na2O SiO2

  6. 10% Al203, 2% ZrO2, 11% PbO, 16%K2O, 0.8% Na2O Glass contact AZS interface, primary ZrO2 Leucite (Al203-K2O-4SiO2) with zirconia nodule Clear Knot Main interest of using HZFC material • low level of Crystallized or vitreous defect origin of defects in convective area as : • Low level of glass contact defects HZFC AZS (41% ZrO2)

  7. Main interest of using HZFC material • low level of blistering at high temperature • Low level of glass contact defects Test condition : TV/PDP glass, Temperature :1450°C, Duration :70H Crucible test AZS (41% ZrO2) HZFC

  8. 2 Low temperature oxygen blistering phenomenon

  9. low temperature oxygen blistering phenomenon • High quality glass  extended use of HZFC materials in the furnace final part (fining, feeder, …) • To solve some corrosion problem (borosilicate, crystal glass …..) • To prevent Glass contact defect related to chemical composition of the glass (compare alpha/béta alumina product, or AZS product ) Oxygen blistering phenomenon

  10. Low temperature oxygen blistering phenomenon • Blistering phenomenon with high efficiency Blistering crucible test at 1120°C , 30 hours , alkali test glass Necessary conditions to obtain high oxygen blistering • Air outside crucible • Temperature < 1130°C • Alkalii inside the glass

  11. Electrical furnace HZ Oxygen blistering in the join ( low temperature area ) 1120°C Low temperature oxygen blistering consequences 1250°C • bubble defect in glass • Corrosion enhancement by upward drilling phenomenon Glass cold area glass

  12. 3 Hypothesis of this phenomenon

  13. Monoclinic zirconia Quadratic zirconia Low temperature oxygen blistering mechanism : High temperature dependence of this phenomenon related to zirconia crystallographic transformation Thermal expansion % Temperature 1120-1140°C

  14. Conductivity process change with zirconia transformation Low temperature oxygen blistering mechanism : Electrical conductivity process change with temperature at the zirconia crystalographic transformation

  15. Arrhenius diagram : Log(sigma) = f(1/T) for zirconia contribution 1/T(K°) 0 0 1E-04 2E-04 3E-04 4E-04 5E-04 6E-04 7E-04 8E-04 9E-04 0,001 0,001 0,001 0,001 0,001 0,002 0,002 0,002 0,002 -2 -4 Activation energy increase after zirconia transformation -6 ER 1195 Ln sigma (ohm-1.cm-1) -8 -10 -12 -14 Low temperature oxygen blistering mechanism : • Electronic to ionic conductivity change at the zirconia temperature transformation

  16. réduction Reaction M Y+ + x e-  M y-x e- Na+, K+ Oxydation 2 O2- O2 + 4 e- Oxygen Blistering mechanism Hypothesis Refractory wall glass • Electro chemical process that can take place because of: • alkali available in the glass • electronic conductivity in the refractory at T<1130°C • oxygen outside of the crucible that could be reduced(or that could reoxydized impurities)

  17. 4 How to prevent low temperature oxygen blistering with HZFC

  18. Y2O3 addition Glass crystallization temperature How to prevent low temperature blistering in glass Deformation % Monoclic zirconia Quadratic zirconia Temperature

  19. How to prevent low temperature oxygen blistering Y2O3 addition that allow to : • lower the electronic conductivity temperature area • Stay stable with temperature • Doesn’t react with alumina or silica inside the glassy phase • Form solid solution with zirconia Microprobe mapping of Y2O3

  20. Y2O3 target = [ 0.8 – 1%] Y2O3 necessary level is related to glass crystallization curve (Higlh quality display panel glass )

  21. Sensible shift of zirconia transformation temperature with Y2O3 addition • Need to adapt the glassy phase composition to the lower reverse temperature transformation during the annealing process of the block

  22. Glassy phase modification with Y2O3 addition Glassy phase properties measurements in the SiO2-Al2O3-Na2O-Y2O3 systemsimulation • Thermal expansion • Glass transition temperature, crystallization • High température viscosity To design the right level of SiO2, Na20 and Al2O3 for a given Y2O3 %

  23. New HZFC materials : First industrial results Cut block Low level of internal defect SiO2 = 4 – 6 %, Al2O3 = 0.7 -1.2 %, Na2O = 0.4- 0.8%, Y2O3 = 0.8 – 1%

  24. Blistering test results on industrial products : Crucible test : 1100°C , 30 hours HZFC High alkalii test glass Display panel glass New HZYFC Display panel glass High alkalii test glass No oxygen bubles with the new product at 1100°C

  25. Blistering test results on industrial products : Crucible test : 1000°C , 30 hours HZFC Display panel glass High alkalii test glass New HZYFC Display panel glass High alkalii test glass • No oxygen blistering up to 1000°C with new HZFC • Secure solution with display panel glass (no blistering up to crystallization temperature)

  26. 5 Glass contact properties

  27. Static corrosion test (T-test) Conditions of the test : Temperature : 1500°C Duration : 48 heures Glass : PDP

  28. Dynamic corrosion test (test MGR) Conditions d’essais : Température : 1500°C Duration : 48 heures Glass : PDP

  29. 6 Influence of crystal glass composition evolution regarding AZS and HZFC materials

  30. Crystal glass composition evolution  Evolution to lead free Glass SiO2 in complement First family : lead free glass with BaO addition, ( increase of Al2O3, CaO, Na2O, decrease of K2O ) Second family: lead free glass without BaO, with main addition of ZnO, TiO2

  31. Glass evolution impact of refractory corrosion Tests conditions : Diameter: 22 mm, height: 100mm Speed: 6 rpm Temperature: 1450°C, duration 72 hours Not working at iso viscosity • Corrosion level increase with lead free crystal glass • Corrosion level with Crystal lead free glass with/without BaO are similar • Lower corrosion resistance of HZFC compared to AZS material (protective interface layer) in condition of high glass interface removal : this is not the case with horizontal interface like in paving or electrode block due to heavy enriched zirconia interface SAMSUNG CORNING 04/98

  32. Glass evolution impact of refractory stoning potential HZFC AZS • Tests conditions • Temperature: 1450°C • Time: 48 hours HZFC AZS Index given from 1 to 5 (1: no stone in drop, 5: lot of crystals in drop)

  33. 200µm 200µm 200µm Lead Crystal glass Lead free Crystal glass HZFC – glass interface No formation of HZFC/Crystal glass interface in each case

  34. 200µm 100µm 200µm 100µm 200µm 200µm Lead Crystal glass Lead free crystal glass AZS – glass interface -Dissolution of alumina from eutectic crystals -Free zirconia crystals

  35. Glass defect coming from AZS material in lead free crystal glass Chemical composition of glass defect

  36. As a conclusion • Glass composition change towards lead free glass • Enhance corrosion level • Doesn’t affect the advantage of using HZFC in terms of defect due to very sharp glass refractory interface • New HZFC solution to avoid low temperature oxygen blistering by modifying ZrO2 electrical properties • Less glass defects at low temperature (oxygen blisters) • Better corrosion resistance without upward drilling phenomenon in join (low temperature area ) • Better filling of the block • Same advantage as conventional HZFC product

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