OPTOCERAMICS Pille, A., Kanaev, A., Chateigner, D., El Mendili, Y., - PowerPoint PPT Presentation

Texte FROM WET SPONGES TO OPTOCERAMICS Pille, A., Kanaev, A., Chateigner, D., El Mendili, Y., Feldbach, E., Billeton, T., Schoenstein, F. Laboratoire de Sciences des Procédés et des Materiaux, Université Paris 13, Sorbonne Paris Cité, Villetaneuse, France , e-mail: annika.pille@lspm.cnrs.fr T02: High Temperature Processes and Advanced Sintering ECerS 2017 Budapest

Topics of discussion • Context and objective • Growing and modifying the “sponges” • Consolidation – spark plasma sintering • Characterization of ceramics • Conclusions and perspectives Micro- Porous SPS grained sponges ceramics bottom-up strategy 11/07/2017 2 Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest

Motivation To control the grain size of ceramics on our way to self-healing nano-grained transparent ceramics Applications as optical windows in nuclear (fusion) power plants, transparent armors, nose cones for heat seeking missiles (YAG), space engineering, medicine … Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 3

Growing alumina monoliths* UPA 99% porosity of the monolith makes it easy to dope by gas or liquid 1 cm/h = 0,5 g ** (43 m% water) 80% humidity, 25°C, cooling plate 23°C TMES Al plate + Ag-Hg amalgam -> Al(OH)3 monolith *Vignes, J. L. et al. J. Mater. Sci. 43 (2008) **Khatim, O. et al. Acta Materialia 71 (2014) Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 4

Spark plasma sintering • Joule effect => fast process, grain size control • High temp + pressure => dense materials 0 600 1200 1800 2400 3000 3600 4200 4800 5400 0 80 Dr. Sinter LAB Series SPS-515S -1 70 -2 Displacement (mm) 60 • Vacuum or argon Pressure (MPa) -3 50 • Conductive or not -4 • 3.5 – 50 kN 40 -5 • 20 – 2000°C 30 • Sample -6 20 displacement -7 0 600 1200 1800 2400 3000 3600 4200 4800 5400 Time (s) C1 pressure C1 displacement Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 5

Alumina ceramics 𝛓 ≈ 100% 2 um 1450° C 20’ @ 80 MPa 1450° C 20’ + 1150 ° C 10’ @ 80 MPa our 𝛿 -alumina commercial 𝛿 -alumina From previous work in LSPM* 𝛓 =97,8% Powder crystallite size: 10 nm Powder crystallite size: 50 nm Although our 𝛿 -alumina powder crystallite size is smaller than the commercial powder’s, the sintered ceramic has bigger grain size *Tõldsepp, E. et al. Ceram. Int. 42 (2016) Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 6

Effect of green body preparation SPS cycle: 3 ’ at 1450°C, 300 MPa 1 um 20 um 2 um our alumina, pre-pressing with 4t our alumina, no pre-pressing 𝛓 =98,6% 𝛓 =96,6% Pre-pressing with 4t for better densification leads to a tenfold increase in grain size Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 7

XRD texture study 5° ×5° grid with 0° ≤ χ ≤55 ° and 0° ≤ ϕ ≤ 355° As received from SPS Post-annealing at 1000°C • Mild fibrous texture aligned with SPS pressure-axis • Crystallite shape “ spherifizes ” during annealing Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 8

Mullite, spinel – reactive sintering SPS cycle: 20’ at 1450 ° C + 10’ at 1150 °C, 100 MPa Our alumina doped with TMES in gas phase OR in liquid phase with Mg(NO 3 ) 2 ∙ 6H 2 O 10 um 2 um 2 um our alumina + Mg(NO 3 ) 2 commercial spinel our alumina + TMES 𝛓 =97,3% 𝛓 =96,5% 𝛓 =3,54 g/cm 3 2 um 1 um • Stoichiometric Al 2 O 3 :MgO ratio gives monophasic spinel ceramic • Average grain size of spinel produced by reactive sintering is about 5 times larger than that of spinel produced from commercial powder via the same cycle. Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 9

Cathodoluminescence study MgAl 2 O 4 ceramics compared to a single crystal* • 1.8 eV -> the R-lines of Cr 3+ impurity** • 2.4 eV -> tetrahedral Mn 2+ impurity** • 2.4 – 4 eV -> F , F + centres + complex intrinsic defects*** • 4.5-6.5 eV -> “ anti- site” defects** *Lushchik et al J. Lum. 102-103 (2003) **Gritsyna et al. Nucl. Instr. and Meth. in Phys. Res. B 250 (2006) ***Sawai, Uchino J. Appl. Phys. 103523 (2012) Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 10

Conclusions • Dense ceramics with various grain sizes and transparencies, starting from UPA • Starting from a phase with smaller crystallite size does not insure a smaller-grained ceramic • Pre-pressing leads to a tenfold increase in grain size • The spinel samples need annealing in air to get rid of coloration • Slight fiber-like texture aligned with the pressure axis of SPS, crystallites more spherical after annealing • High inversion level for spinels and common impurities Annika Pille annika.pille@lspm.cnrs.fr ECerS 2017 Budapest 11/07/2017 11

Thank you for your attention! annika.pille@lspm.cnrs.fr LSPM-CNRS Université Paris 13 99 Av J. B Clément 93430 Villetaneuse, France www.lspm.cnrs.fr Fax: +33 1 49 40 34 14 Acknowledgements: Université Paris 13 EUROfusion