Della Negra, Michela

Knöfel, Christina

Thydén, Karl Tor Sune

Wandel, Marie

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 20, 2017Study of the behaviour of YSZ dispersions in waterDella Negra, Michela; Knöfel, Christina; Thydén, Karl Tor Sune; Wandel, MariePublication date:2011Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Della Negra, M., Knöfel, C., Thydén, K. T. S., & Wandel, M. (2011). Study of the behaviour of YSZ dispersions inwater. Poster session presented at 12th Conference of the European Ceramic Society, Stockholm, Sweden.Support by EUDP under the project ENS-64010-0052 “Fuel cells put to work”Help in the Raman analysis by C. PardanaudContribution with ICP analysis by P.  RoosPoster graphics by S. BrinkWe gratefully acknowledge:Atomic percentage from E DS analysis S ample Y at % Zr at%  Y /Zr Raw material 17.6±1.5 82.4±1.9 0.21±0.02 1 hour milling centrif. 19.1±1.6 80.9±2.1 0.24±0.03 1 hour milling oven (1)  11.7±3.2 88.3±4.3 0.13±0.04 1 hour milling oven (2)  21.8±3.1 78.2±4.1 0.28±0.05 1 hour milling oven (3)  16.7±1.6 83.3±2.1 0.20±0.02 3 days milling centrif.  19.6±1.8 80.4±2.3 0.24±0.03 3 days milling,oven 18.4±1.4 81.6±1.8 0.22±0.02 Raw powder1 h milling3 days millingRaman spectroscopyExperimental details8% yttria stabilized zirconia milled in water for:1 hour, 1 day, 3 days.Solid load: 40% in mass2 drying procedures were tested:Centrifugation and drying at RTDrying in ovenThe particles were analysed with: Raman spectroscopy,  EDS and XPS (results not shown because inconclusive)Treatments in native pHConclusions:Y   is leaching from the cubic structure in aqueous acidic solutions. Zr   is leaching at pH=1,  in smaller extent than Y  . The amount of Zr   in solution is low in the entire pH rangeZeta potential and pH of the dispersion change with time, showing that the particle surface and the solutions are modified. The equilibrium is reached in 1-2 days, depending on the pH.The YSZ particle structure and overall composition are not affected.Horiba Jobin Yvon HR800 UV.  Green Argon laser 514 nm.There is no evidence of new features appearing ordisappearing as effect of a new phase formation or adsorption/desorption on the particle surface.   In spite of the data scattering, the results of EDS analysisindicate no change in the atomic ratio between Y and Zr induced by the milling treatments in water or the drying procedure.explored.3+4+ 3+4+Possible issues in suspension stability during processing.pH(i) = 1.2 pH(i)  = 4.9 pH(i) = 8.0 pH(i) = 12.0 pH(i) = 13.2pH(f ) = 1.3 pH(f )  = 5.5 pH(f ) = 7.5 pH(f ) = 11.8 pH(f ) = 13.1YSZ solid load: 40% in mass.pH adjusted with HCl or NaOH3 weeks treatment Long term treatmentsin water at different pH10-610-510-410-310-210-1100101102Concentration (mM)14131211109876543210pH10-1100101102103104105Molar ratio Y/Zr Yttrium Zirconium Molar ratio Y/Z rMolar ratio Y/Zr in YSZY and Zr concentration in the supernatantY    dissolves in water in acidic environment. The amount of Y    found in the supernatantincreases with acidity.Zr    leaches in solution only at low pH.In basic condition the amount of the two elementsin solution is extremely low.Supernatant and powder separated by centrifugation Liquid phase analyzed with ICP In the acidic range the molar ratio Y/Zrin the supernatant is muchhigher than it is in theYSZ powder,provingactualdissolution  3+4+3+Motivations: Better understanding of the behaviour of yttria fully stabilized zirconia in water for applications in wet ceramic processingQuestions:Are Y   and Zr   leaching in solution from the cubic structure?Is the particle surface affected?Are the particle structure and composition affected?3+ 4+Properties of the Y SZ powder Specific surface area 12.9 m2/g Cryst allite size 23 nm Particle size (d50) 0.15 µm ZrO2 ( Mass %)  86.3% Y 2O3 (Mass %)  13.6% Na2O ( Mass %)  0.07%  14 1413 1312 1211 1110 109 98 87 76 65 54 43 32 21 10 0pH1800150012009006003000Time elapsed from preparation (min)Evolution of pH with time Initial solution pH = 1. 1 Initial solution pH = 5. 9 Initial solution pH = 12.9806040200-20-40Zeta Potential (mV)131211109876543pHIEP=10.2Increasing pHDecreasing pHTitration YSZ806040200-20-40Zeta Potential (mV)2700240021001800150012009006003000Time elapsed from preparation (min) Initial pH = 1 Initial pH = 5 Initial pH = 13Evolution of Zeta Potential with tim eIsoelectric pointYSZ milled in water for 3 daysTitrations performed with:HCl 0.2 M and NaOH 0.2 MSolid load: 13% in massZeta potential increases with time and reaches a plateau for native pH and pH=1.Potential ishigher at low pH and increases faster.In basic solution the potential is negative and decreases with time. The suspension is not stableand the powder tends to sediment in spite of energic stirring. The powder acts as a base or as an acid (depending on the conditions) modifying the suspension pH.The pH reaches stability with time.Powder potential and suspension pHYSZ immersed in the solutions, solid load: 40% in mass.Initial pH adjusted with HCl and NaOH20 um200 nmYZrOOxygenvacancy3+4+2-M. Della Negra, C. Knöfel, K.  Tydén, M. WandelSTUDY OF THE BEHAVIOUR OF YSZ DISPERSIONS IN WATER STUDY OF THE BEHAVIOUR OF YSZ DISPERSIONS IN WATER

Study of the behaviour of YSZ dispersions in water

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Study of the behaviour of YSZ dispersions in water

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