1 / 29

Silicon nitride based ceramics – Materials for extreme environments - Corrosion in molten FLiNaK

Silicon nitride based ceramics – Materials for extreme environments - Corrosion in molten FLiNaK. M. Hnatko , 1 P. Šajgalík, 1 Z. Lenčéš, 1 V. Petrušková , 1 M. Kašiarová, 2 R . Klement 2. 1 Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava, Slovakia

marjoriez
Download Presentation

Silicon nitride based ceramics – Materials for extreme environments - Corrosion in molten FLiNaK

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Silicon nitride based ceramics – Materials for extreme environments - Corrosion in molten FLiNaK M. Hnatko,1 P. Šajgalík,1 Z. Lenčéš,1 V. Petrušková,1 M. Kašiarová,2R. Klement2 1 Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava, Slovakia 2 Institute of Materials Research, Slovak Academy of Sciences, Košice, Slovakia

  2. Motivation Application of molten inorganic materials: • FLiNaK: 46.5 mol% LiF, 11.5 % NaF, 42% KF • Aluminium industry • Electrolite for cathodic deposition of TiB2, ZrB2, MSix, Mo, Nb • Heat transfer applications (good l, high Cp, low h, high Tb) • Solar thermal energy storage • Nuclear energy (primary reactor coolant) • Molten salt reactors (fuel FLiNaK+ZrF4+UF4, coolant)

  3. Motivation Advanced High Temperature Reactor & Hydrogen production Forsberg C. W., Developments in Molten Salt and Liquid-Salt-Cooled Reactors, Proceedings of ICAPP 06, Reno, Nevada USA, June 4-8, 2006, paper6292.

  4. Motivation

  5. Motivation FLiNaK Disadvantage: highly corrosive medium Superalloys: Hastelloy-N,Hastelloy-X, Haynes-230, Inconel-617, Incoloy-800H • Ceramics: • containers of molten salts • sensors in molten salt baths

  6. Experimental SiAlON:Si6-zAlzOzN8-z, z = 4 SNY: Si3N4+ 5 wt% Y2O3 1700C/1h/30 MPa 600 rpm/2h IPA >25 mm

  7. XRD analysis b-Si3N4

  8. XRD analysis from unit cell: z = 3.6

  9. SNY SiAlON Microstructural analysis 1 mm 2 mm

  10. Experimental Sample holder Test bars FLiNaK: LiF 46.5% NaF 11.5% KF 42.0% samples FLiNaK Conditions: 1 = 48 h 2 = 96 h 3 = 192 h T = 580 °C N2 atmosphere (3x4x60 mm)

  11. N2 N2 Experimental set-up

  12. FLiNaK SiAlON t = 0 min T = 25 C t = 0 min T = 580 C t = 10 min T = 580 C Wetting of SiAlON by FLiNaK

  13. Results of corrosion test SiAlON-F SNY-F

  14. Si3N4 - FLiNaK 48 h

  15. 48 h 96 h 20 mm 20 mm 192 h 10 mm

  16. EDX and XRD analysis 2 Date: 22.3.2010 13:07:19 HV: 20,0 kV Puls th.: 7,24 kcps El AN Line unn. C norm. C Atom. C [mass %] [mass %] [At.%] -------------------------------------------- Si 14 K-series 43,24 37,46 33,13 N 7 K-series 25,11 21,76 38,59 Y 39 L-series 18,48 16,01 4,47 Au 79 M-series 11,54 10,00 1,26 O 8 K-series 8,20 7,10 11,03 F 9 K-series 4,86 4,21 5,50 C 6 K-series 3,01 2,61 5,40 K 19 K-series 0,72 0,62 0,40 Al 13 K-series 0,27 0,23 0,22 --------------------------------------------- Total:: 115,4 % a = 12 h = 30 mm

  17. SiAlON - FLiNaK

  18. Cross section of samples after corrosion test 48 h surface 48 h surface 96 h 192 h surface

  19. 1 Date: 24.3.2010 8:00:044 HV: 20,0 kV El AN Line unn. C norm. C Atom. C [mass %] [mass %] [At.%] -------------------------------------------- Al 13 K-series 50,81 37,41 29,29 O 8 K-series 29,71 21,88 28,88 N 7 K-series 24,96 18,38 27,71 Si 14 K-series 21,69 15,97 12,01 Au 79 M-series 7,29 5,37 0,58 C 6 K-series 0,89 0,65 1,15 F 9 K-series 0,47 0,35 0,38 --------------------------------------------- Total:: 135,8 % 2 Date: 24.3.2010 8:01:055 HV: 20,0 kV El AN Line unn. C norm. C Atom. C [mass %] [mass %] [At.%] -------------------------------------------- Al 13 K-series 44,19 36,58 28,50 O 8 K-series 26,90 22,27 29,25 N 7 K-series 21,88 18,12 27,18 Si 14 K-series 16,79 13,90 10,40 Au 79 M-series 7,18 5,94 0,63 F 9 K-series 2,93 2,42 2,68 C 6 K-series 0,93 0,77 1,35 --------------------------------------------- Total:: 120,8 % EDX analysis SiAlON-F after 48 h

  20. EDX analysis 1 Date: 30.3.2010 10:40:59 HV: 20,0 kV Puls th.: 6,33 kcps El AN Line unn. C norm. C Atom. C [mass %] [mass %] [At.%] -------------------------------------------- O 8 K-series 29,19 26,90 37,18 F 9 K-series 28,12 25,92 30,17 K 19 K-series 19,43 17,90 10,13 Al 13 K-series 12,34 11,37 9,32 Si 14 K-series 10,88 10,03 7,89 Au 79 M-series 5,43 5,01 0,56 C 6 K-series 2,46 2,27 4,17 Na 11 K-series 0,66 0,60 0,58 --------------------------------------------- Total:: 108,5 % Sample surface after 96h 3 Date: 30.3.2010 10:42:20 HV: 20,0 kV Puls th.: 6,96 kcps El AN Line unn. C norm. C Atom. C [mass %] [mass %] [At.%] -------------------------------------------- O 8 K-series 38,78 37,55 51,59 K 19 K-series 16,64 16,12 9,06 Al 13 K-series 15,92 15,42 12,56 Si 14 K-series 14,35 13,89 10,87 F 9 K-series 9,58 9,28 10,73 Au 79 M-series 5,40 5,23 0,58 C 6 K-series 2,59 2,51 4,60 --------------------------------------------- Total:: 103,3 %

  21. XRD analysis of the surface layer a = 1 h = 3 mm a = 12 h = 30 mm

  22. Bending strength of corroded SNY samples Si3N4 samples SiAlON samples

  23. FLiNaK + K2NaAlF6+KAlSiO4 corrosion of GB & matrix phase (slow) Improvement of strength of SiALON samples after coorosion 48 h 96 h 192 h healing of surface defects? FLiNaK

  24. FactSage 5.5 thermochemical software and databases Gas phases: SiF4, SiF3, SiF2, SiO K, Na, Li NaAlF4, LiAlF4, Na2AlF5, AF3, Li2AlF5 KF, LiF, NaF Liquid phases: KF, LiF, NaF K2O, Na2O, Li2O Solid phases: K3AlF6, K2Al12O19 KAlSiO4 Thermodynamic background 1 mol FLiNaK, 0.02 mol Si3N4, 0.04 AlN, 0.04 Al2O3 400-1300ºC, 0.1 MPaN2

  25. YF3 (s,l) corrosion of GB phase (faster) Corrosion of SNY samples Si3N4+5 wt% Y2O3 FLiNaK SiF4(g)

  26. Thermodynamic background Si3N4:FLiNaK= 1:10 400-1300ºC, 0.1 MPaN2

  27. Thermodynamic background Si3N4:FLiNaK= 1:10, 400-1300ºC, 0.1 MPaN2 Si3N4(s) + 12 KF(l) = 3 SiF4(g) + 12 K(g) + 2 N2(g) Y2O3 + 6 KF = 2 YF3 + 3 K2O SiO2 + 4 KF = SiF4 + 2 K2O

  28. Thermodynamic background

  29. Conclusions • both SNY and b-SiAlON ceramic materials have • a good corrosion resistance against FLiNaK • the corrosion of SNY proceeds preferentially through the GB • the corrosion of b-SiAlON is slower in FLiNaK a proceeds • across the bulk material • (the corrosion rate of matrix and GB phase is comparable) • both ceramics can be applied in the field of fluorine-based • molten salts (b-SiAlON has a better corrosion resistance)

More Related